Rainbow ( mykiss): A Technical Conservation Assessment

Prepared for the USDA Forest Service, Rocky Mountain Region, Conservation Project

October 10, 2008

W. Linn Montgomery1 and Yael Bernstein1,2

1 Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011-5640 2 SWCA Environmental Consultants, 114 N. San Francisco St. #100, Flagstaff, AZ 86001 Peer Review Administered by American Society Bernstein, Y. and W.L. Montgomery. (2008, October 10) (Oncorhynchus mykiss; Walbaum, 1792): a technical conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Available: http://www.fs.fed.us/r2/projects/scp/assessments/rainbowtrout.pdf [date of access].

ACKNOWLEDGMENTS

We thank Richard Vacirca, Gary Patton, and David Winters of the USDA Forest Service Rocky Mountain Region for the opportunity to prepare this assessment and for their assistance at many points in its preparation and finalization. Thanks are also due an anonymous reviewer for many helpful comments.

AUTHORS’ BIOGRAPHIES

W. Linn Montgomery received B.A., M.A., and Ph.D. degrees from the UC Berkeley, UCLA, and Arizona State University, respectively. As a postdoctoral researcher with Woods Hole Oceanographic Institution, he studied the ecology of Atlantic and sea-run in eastern before joining the faculty at Northern Arizona University. From 1984 to 1987, he served on, and in 1986 chaired, the Arizona Game and Commission. He also served as Commission representative to the Arizona Water Quality Control Council and various committees of the Western Association of Fish and Wildlife Agencies. His students have studied rainbow trout, , , native and exotic cyprinids, marine surgeonfishes, damselfishes and scorpionfishes, rattlesnakes, ephemeral pond , , ecology, and fish paleontology. His personal research interests focus on feeding ecology and physiology of herbivorous , including work on their lipid dynamics and gut microbes, and reproductive ecology of salmonids and marine reef fishes.

Yael Anna Bernstein received B.S. degrees in both Microbiology (with a Minor in Chemistry) and Finance and Computer Information Systems from Northern Arizona University; she has completed portions of a Masters degree program in Biology with an aquatic ecology focus. She has 11 years of experience with scientific monitoring and research trips in Grand Canyon, and she has worked for Northern Arizona University as a cooperator with the Grand Canyon Monitoring and Research Center from 2002 to 2005. She has direct experience with issues related to native and nonnative fish studies in the Southwest and is experienced in field sampling techniques, data analysis, and laboratory analyses, including food studies and otolith work.

COVER PHOTO CREDIT

Photograph of rainbow trout (Oncorhynchus mykiss) by E.R. Keeley, used with permission.

2 3 SUMMARY OF KEY COMPONENTS FOR CONSERVATION OF THE RAINBOW TROUT

Status

The Rocky Mountain Region (Region 2) of the USDA Forest Service is beyond the native range of the rainbow trout (Oncorhynchus mykiss). Populations in Region 2 were established by introductions from for recreation and market purposes, and it is not considered a federally or state threatened, endangered, or sensitive species (U.S. Fish and Wildlife Service; http://endangered.fws.gov/). Elsewhere in its native range, several populations of rainbow trout are federally listed as threatened or endangered. However, this is not likely to influence the status of populations in Region 2, where the species is common in streams and and populations are maintained either through self-sustaining natural reproduction or through various levels of supplemental stocking of fish where self- sustaining populations do not occur. Natural or anthropogenic alteration of may lead to declines in individual populations, as may changes in management practices intended to protect native species; otherwise, the rainbow trout should be considered secure within Region 2.

Primary Threats

As noted above, there are no native stocks of rainbow trout in Region 2. Nonetheless, existing stocks in the Region face the potential for population declines under the influence of both natural and human threats that alter or destroy habitat. Addressed more specifically elsewhere in this assessment, these threats include, but are not limited to, reduction of stream discharge, and changes in water temperature, water quality, substrate, and food base. In addition, perpetuation of some existing populations and future development of new populations to support demand will take place against a backdrop of concerns over conservation or recovery of native fishes and their , which are documented in other assessments in this series. Such constraint was not in place when many of the existing rainbow trout populations were established.

Primary Management Elements, Implications and Considerations

Rainbow trout in the Rocky Mountain Region are an introduced, nonnative species capable of occupying a wide array of habitats, feeding on virtually any of nutritionally valuable , and hybridizing with native trout that may be the focus of recovery efforts. This ecological flexibility has allowed them to join native faunas throughout the and the world, where they often alter relationships among members of the receiving fauna.

Persistence of rainbow trout populations in Region 2 will depend on persistence of water quality and quantity sufficient to maintain the existing coolwater they presently occupy. Populations presently maintained by stocking of catchable-size trout (in support of a “put-and-take” management strategy) or fingerlings (for a “put-grow- take” strategy) could be enhanced by providing additional spawning, fry, or juvenile habitat. Such actions could also reduce management costs by shifting the age and size of stocked fish toward earlier life history stages or by relying more on natural spawning.

2 3 TABLE OF CONTENTS

ACKNOWLEDGMENTS ...... 2 AUTHORS’ BIOGRAPHIES ...... 2 COVER PHOTO CREDIT ...... 2 SUMMARY OF KEY COMPONENTS FOR CONSERVATION OF THE RAINBOW TROUT ...... 3 Status...... 3 Primary Threats...... 3 Primary Management Elements, Implications and Considerations ...... 3 LIST OF TABLES AND FIGURES ...... 6 INTRODUCTION ...... 7 Goal...... 7 Scope...... 7 Treatment of Uncertainty ...... 8 Application and Interpretation Limits of This Assessment...... 8 Web Publication ...... 9 Peer Review ...... 9 MANAGEMENT STATUS AND NATURAL HISTORY ...... 9 Existing Regulatory Mechanisms, Management Plans, and Conservation Strategies...... 9 Biology and Ecology...... 16 Systematics...... 16 Species description...... 18 Salmonid life history characteristics ...... 18 Distribution and abundance...... 19 Population trends (local, regional, and rangewide)...... 20 Activity patterns ...... 21 Habitat ...... 23 Spawning habitat ...... 23 Nursery habitats – incubation and fry rearing ...... 25 Fry habitat...... 25 Juvenile habitat...... 26 Adult habitat ...... 27 Overwinter habitat...... 28 Food habits ...... 28 Breeding biology...... 30 Demography...... 32 Genetic characteristics and concerns...... 32 Additional concerns with hybridization ...... 33 Social patterns for spacing ...... 33 Pattern of dispersal of young and adults ...... 34 Limiting factors...... 34 Predators...... 34 Competitors ...... 34 Parasites and disease ...... 38 Symbiosis ...... 42 MANAGEMENT AND CONSERVATION ...... 42 of Rainbow Trout in the Rocky Mountain Region...... 42 Potential Threats to Trout Populations...... 42 Anthropogenic disturbance ...... 42 Agriculture...... 42 Logging for timber and for water ...... 44 Mining ...... 44 Roads, road construction, stream channelization, population fragmentation...... 44 Aquatic hitchhikers/nuisance ...... 44 4 5 Energy development...... 45 Chemical ...... 45 Dams...... 46 Excessive harvest...... 46 Changes in water temperature ...... 46 Outdated water rights systems...... 47 Instream flow...... 48 in wilderness and other protected areas ...... 49 Natural disturbance ...... 50 Drought...... 50 Fire...... 50 Scour (extracted from Schuett-Hames et al. 1996) ...... 52 ...... 52 Management of Rainbow Trout in Region 2...... 53 Implications and potential conservation elements ...... 53 Rainbow and native fishes...... 53 Tools and practices ...... 54 Rainbow trout as a Management Indicator Species ...... 54 Management approaches ...... 56 Roles of hatcheries in fisheries and conservation...... 57 Information Needs...... 66 REFERENCES ...... 69

EDITORS: Richard Vacirca and David Winters, USDA Forest Service, Rocky Mountain Region

4 5 LIST OF TABLES AND FIGURES

Tables: Table 1. Game and Fish state-wide trout stream classification system...... 16 Table 2. Scientific nomenclature for rainbow trout...... 17 Table 3. Original ranges and considered within Oncorhynchus mykiss...... 21 Table 4. Spawning habitat for western trout and ...... 23 Table 5. Known foods of rainbow trout...... 29 Table 6. Known or likely predators of rainbow trout, including steelhead...... 35 Table 7. Recent reports of known, likely, and unlikely competitors of rainbow trout...... 36 Table 8. Major groups of parasites recorded from Wyoming fishes...... 39 Table 10. Relationship between life history stage of a fish and the likelihood that stage may transmit whirling disease...... 41 Table 9. Susceptibility to whirling disease among species of salmonids...... 41 Table 11. Federal and non-federal fires in the Rocky Mountain area, FY 2005...... 50 Table 12. Fishes raised in Region 2 state and federal hatcheries...... 59 Table 13. Post-stocking survival rates for rainbow trout stocked in North American waters...... 60 Table 14. Summary of rainbow trout stocking rates reported in various North American jurisdictions...... 66

Figures: Figure 1. Native ranges of several western trout species and subspecies in the and ...... 8 Figure 2a. National forests and grasslands of ...... 10 Figure 2b. National forests and grasslands of Kansas...... 11 Figure 2c. National forests and grasslands of Nebraska...... 12 Figure 2d. National forests and grasslands of South Dakota...... 13 Figure 2e. National forests and grasslands of Wyoming...... 15 Figure 3. Native distribution of rainbow trout in the United States...... 20 Figure 4. Distribution and conservation status of rainbow trout in the United States...... 22 Figure 5. Rainbow trout fecundity related to weight...... 31 Figure 6. Life cycle of the whirling disease parasite...... 40 Figure 7. Fire threats and drought in the western United States...... 51

6 7 INTRODUCTION fish, and quite localized management directives in some cases, we do not attempt a catalog of locales, sources of This assessment is one of many being produced to fish, or regulations on a local scale within the states. support the Species Conservation Project for the USDA Forest Service (USFS) Rocky Mountain Region (Region The primary foci of this report deal with rainbow 2), which encompasses the national forests and national trout biology, their possible interactions with sensitive grasslands in Colorado, Kansas, Nebraska, South native cutthroat (Oncorhynchus clarkia) (e.g., Dakota, and Wyoming. The rainbow trout (: greenback (O. c. stomias), Colorado Oncorhynchus mykiss; also called in some River cutthroat trout (O. c. pleuriticus), Yellowstone regions) is the focus of this assessment because it is a cutthroat trout (O. c. bouvieri), cutthroat Management Indicator Species (MIS) on a number of trout (O. c. virginalis); Figure 1), and real or potential national forests within Region 2. As an MIS, it serves threats facing existing rainbow trout stocks within as a barometer for species viability at the forest level. Region 2. This report should provide agencies with a Management Indicator Species have two functions: 1) better understanding of the rainbow trout and the sport to estimate the effects of planning alternatives on fish fishing opportunities it provides or might provide under and wildlife populations (Title 36, Code of Federal different management practices. Regulations 219.19 [Planning - Ecological, social, and economic sustainability] (a) (1)); and 2) to monitor the Scope effects of management activities on species via changes in population trends (36 CFR 219.19 (a) (6)). The The rainbow trout assessment examines the primary goal of this assessment is to provide the USFS biology, ecology, conservation status, and management and other federal (e.g., Bureau of Land Management, of this species with specific reference to the geographic U.S. Fish and Wildlife Service (USFWS), Bureau and ecological characteristics of the USFS Rocky of Reclamation) and state agencies with information Mountain Region where possible. Although most about the primary threats to naturally-reproducing of the massive literature on this species (a search rainbow trout populations in the wild as well as of Cambridge Scientific Abstracts, June 2008, for stocked (hatchery-raised) rainbow trout in designated references with ‘rainbow trout’ as keywords yielded recreational fisheries. This information will facilitate 15,858 citations) originates from investigations outside further evaluation of rainbow trout in Region 2, leading the region, this document places that literature in the to decisions by the agency regarding its conservation ecological and social contexts of the central Rocky and management status. Mountains. Similarly, this assessment is concerned with reproductive behavior, population dynamics, and Goal other characteristics of rainbow trout in the context of the current environment rather than under historical Species conservation assessments produced as conditions. The native environment of the species is part of the Species Conservation Project are designed considered in conducting the synthesis, but it is placed to provide forest managers, research biologists, and in a current context. the public with a thorough discussion of the biology, ecology, conservation status, and management of In producing the assessment, we reviewed certain species based on available scientific knowledge. refereed literature, non-refereed publications, research The assessment goals limit the scope of the work to reports, and data accumulated by resource management critical summaries of scientific knowledge, discussion agencies. Many of the references we used came from of broad implications of that knowledge, and outlines studies beyond Region 2, but the behavioral and of information needs. The assessment does not seek ecological plasticity of rainbow trout make it likely to develop specific management recommendations. that patterns seen elsewhere could appear under Rather, it provides the ecological background upon similar circumstances in the Region. Not all published which management must be based and focuses on the materials should be considered equally reliable, so we consequences of changes in the environment that result have emphasized refereed literature in the assessment. from management (i.e., management implications). Nonetheless, data not subjected to peer review (e.g., We also summarize management practices or fisheries Natural Heritage Program records, NatureServe reports, regulations that relate to rainbow trout of the states in various “gray literature” reports) were important in Region 2. Given the present ubiquity of the in describing the geographic distribution and many other a wide array of aquatic environments, its origins and aspects of the biology of the species. often persistence due to stocking of hatchery-reared 6 7 Figure 1. Native ranges of western trout species and subspecies in the western United States and Canada. From: The Western Native Trout Campaign, www.westerntrout.org/trout/index.htm.

Treatment of Uncertainty The animal that is the subject of this assessment exhibits tremendous plasticity in its ability to deal This assessment is based on information reported with varied environmental demands and challenges by a wide array of organizations and individuals. in recent ecological time or much longer evolutionary As such, the strength of the available information in time. Nonetheless, it is not difficult to summarize this terms of its accuracy and precision depends on many variability into a general description of the norms of factors, including when work was done, prevailing life for rainbow trout. Therefore, those establishing concepts at that time, the experience of and resources or managing stocks of rainbow trout outside of their (e.g., time, assistance, instrumentation) available to normal range should understand something of the those collecting the information, the potential for doing “normal” pattern as well as the potential variation that manipulative experiments as opposed to relying entirely may be expressed in a particular location or stock. on observations made in field or laboratory, and the nature and quantity of detail desired by those driving Application and Interpretation Limits a particular study. These and other factors compound of This Assessment the inherent uncertainty in living systems that traces to variability due to both biotic and abiotic influences Information used in this assessment was collected on populations, communities, and ecosystems in a from studies that were conducted throughout the native particular location. and introduced geographical ranges of this species as

8 9

106 well as with a number of hatchery populations. Although number does not include several hybrids; Johnson and most information should apply broadly throughout the Nomanbhoy 2005). range of the species, it is likely that certain life history parameters (e.g., growth rate, longevity, spawning time) Colorado contributes more than 66 percent of the will differ in different locales and along environmental acreage (14,490,000 of 26,104,000 acres) of National gradients. Thus, information regarding conservation Forest System Lands in Region 2 (USDA Forest or management strategies for the species may pertain Service 2006) (Figure 2a). The diverse array of habitats specifically to Region 2 and not apply to other portions contained in this area offers opportunities to catch of the species’ range. roughly 80 species, subspecies, or hybrids of warm- and from 6,000 miles of and streams Web Publication (major rivers include portions of the Colorado, Rio Grande, , and South Platte Rivers; http://www. Species assessments in the Species Conservation enchantedlearning.com) and more than 2,000 lakes and Project are being published on the Region 2 World Wide reservoirs (http://wildlife.state.co.us/Fishing/, 2008). Web site (www.fs.fed.us/r2/projects/scp/assessments/ Included in this array of aquatic systems are waters index.shtml). Placing the documents on the Web makes on 13 national forests. All or much of the Arapaho, them available to agency biologists and the public Grand Mesa, Gunnison, Medicine Bow (also see more rapidly than publishing them as reports. More Wyoming, below), Pike, Rio Grande, Roosevelt, Routt, important, Web publication facilitates revision of the San Isabel, San Juan, Uncompahgre and White River assessment, which will be accomplished based on the national forests and a small portion of the -centered guidelines established by Region 2. Manti-La Sal National Forest’s Moab Ranger District (administered by Region 4) and two national grasslands, Peer Review the Comanche and Pawnee national grasslands.

Assessments developed for the Species As the agency primarily responsible for managing Conservation Project have been peer reviewed the state’s fish resources, the Colorado Division of prior to release on the Web. Peer review for this Wildlife (CDOW) operates 14 coldwater hatcheries or assessment was administered by the American rearing units (15 if one includes the Mt. Ouray hatchery Fisheries Society, employing recognized experts operated by Mt. Shavano Hatchery personnel) and for this or related taxa. Peer review was designed two warmwater hatcheries. Two USFWS hatcheries to improve the quality of communication and to supplement total Colorado hatchery output. In 2005, increase the rigor of the assessment. CDOW and USFWS hatcheries stocked more than 3.64 million catchable coldwater fishes (3.57 million MANAGEMENT STATUS AND of which were rainbow trout), 13.4 million fingerling NATURAL HISTORY coldwater fishes (6.07 million rainbow trout fingerlings), 54.5 million warmwater sport fishes, and almost 96,000 individuals of species considered at risk (Federal or Existing Regulatory Mechanisms, State Endangered, Threatened or Special Concern) (U.S. Management Plans, and Conservation Fish and Wildlife Service 2005). The daily bag limit for Strategies most salmonids, which includes rainbow trout, ( trutta), brook trout ( fontinalis), We developed state summaries from print and cutthroat trout (with several subspecies), World Wide Web sources produced by individual (Oncorhynchus mykiss aguabonita), states and by both Region 2 and national programs trout (S. namaycush), ( x brook trout of the USFS. Links to maps for each state are ), Arctic charr (S. alpinus), grayling ( on the USFS Roadless Area Conservation website arcticus), (O. tshawytscha), and (http://roadless.fs.fed.us/). Names of fishes follow kokanee (O. nerka; landlocked ), in Nelson (2006). aggregate is four, with the limit for possession being eight. Exceptions are limits of 10 for both brook trout Colorado and Wyoming together contribute less than 8 inches and kokanee. Statewide, 168 miles of more than 90 percent of the total acreage (23,747,000 Gold Medal streams (i.e., waters offering the greatest of 26,219,000 acres) of National Forest System Lands potential for trophy trout fishing) provide in Region 2. Collectively these states provide homes opportunities for large trout and are managed to ensure for at least 109 species and subspecies of fishes (this populations of big fish. There are many locale-specific 8 9 Figure 2a. National Forests and Grasslands of Colorado. From: http://www.roadless.fs.fed.us/states/co/state3.shtml. regulations as well; the pamphlet describing fishing where fishing is by artificial and lures only, and all regulations for 2008 includes 67 pages of specific cutthroat must be returned to the water immediately. regulations on fishing and other uses. CDOW provides a variety of fishing related Regulations also disallow take of a number of programs such as a June weekend of free fishing for threatened or endangered aquatic species, including residents and non-residents, and Colorado residents 64 bonytail ( elegans), Colorado pikeminnow and older fish free. The state maintains lists of record fish ( lucius), (G. cypha), of many species by weight and, for released fish taken (Xyrauchen texanus), Arkansas by anglers participating in its Master Angler program, darter (Etheostoma cragini), Rio Grande sucker by length. Colorado’s record rainbow trout was taken (Catostomus plebeius), brassy (Hybognathus from Morrow Point Reservoir (Gunnison County) in hankonsoni), common shiner (Luxilus cornutus), river 2003 by Lee Cox; it weighed 19 lbs. 10 oz. and was shiner (Notropis blennius), northern redbelly dace 34 inches long. However, a 40-1/4 inch fish caught and (Phoxinus eos), southern redbelly dace (Phoxinus released by Tony Felicilda in the Taylor River would erythrogaster), plains minnow (Hybognathus placitus), likely have exceeded the present weight record. suckermouth minnow (Phenacobius mirabilis), lake chub (Couesius plumbeus), speckled The Cimarron National Grassland is the only chub (Macrhybopsis tetranema), greenback cutthroat National Forest System property in Kansas, and its trout and boreal toad (Bufo boreas boreas). To 108,000 acres make it the smallest System holding accommodate the growing number of cutthroat streams among the five Region 2 states (Figure 2b). Most of and lakes included in conservation and recovery actions the 10,000 miles of streams and rivers in Kansas (major for greenback cutthroat trout, CDOW has identified rivers include all or portions of the Kansas, Republican, protected Cutthroat Conservation and Recreation waters Smoky Hill, Arkansas, and rivers; http://www 10 11 Figure 2b. National Forests and Grasslands of Kansas. From: http://www.roadless.fs.fed.us/states/ks/state3.shtml.

.enchantedlearning.com) are privately owned, and over in selected waters throughout the state. Rainbow trout 150,000 privately-owned farm ponds in Kansas provide stocked in the Cimarron National Grassland are outstanding fishing opportunities. There are also 24 introduced to impounded waters or fishing pits. In the large reservoirs, 40 state fishing lakes, and more than 1950’s, the fishing pits were hand dug for the purpose 200 community lakes. of attracting waterfowl; they were later stocked with rainbow trout and other game fishes as recreational The Kansas Department of Wildlife and Parks fishing interest increased (Chappell 2006). During the (KDWP) operates four hatcheries and a rearing pond summer months, these fishing pits are stocked with to support stocking Kansas waters; there are no channel , bass, and grass (also known as National Fish Hatcheries in Kansas. In 2005, Kansas white ); rainbow trout from a hatchery near Boulder, hatcheries produced 74.6 million warmwater fishes, Colorado are introduced in the fall to further diversify including bluegill (Lepomis macrochirus), channel the angling experience and to provide a winter catfish Ictalurus ( punctatus), Colorado pikeminnow, (Progress and Management Report 2005, provided by (Ctenopharygodon idella), largemouth Lowell Aberson). Planted trout rarely survive into the bass ( salmoides), paddlefish Polyodon ( hot summer months because of high fishing pressures spathula), pallid (Scaphirhynchus albus), and high temperatures; the pits are isolated from the redear sunfish (L. microlophis), sauger ( Cimarron River and thus are occasionally dry under canadencsis), saugeye (sauger x walleye hybrid), drought conditions. The Kansas trout season runs from (M. dolomieu), striped bass (Morone October 15 to April 15, with a daily creel limit of five saxatilis), wiper (white bass [M. chrysops] x striped trout and 15 total trout in possession. The state record bass hybrid), and walleye (S. vitreus); other species rainbow trout, 9 lb. 5 oz. and 28-1⁄4 inches long, was reared in state hatcheries include (Pomoxis captured on a crappie jig in Lake Shawnee by Raymond spp.) and ( lucius) (U.S. Fish Deghand on November 14, 1982. and Wildlife Service 2005). Special fishing-related programs offered by the KDWP are a trout program, USFS Region 2 manages 352,000 acres among an urban fishing program, the Fishing Forecast, and an three areas in Nebraska, the Nebraska and Samuel R. up-to-date fishing report. McKelvie national forests and the Ogallala National Grassland. The Nebraska Game and Parks Commission Kansas State hatcheries do not produce rainbow (NGPC) regulates fishing throughout the state. trout, but the KDWP does stock and manage this species 10 11 Nebraska is well known for its reservoir fishing. privately constructed lakes, private sandpits, and private Lake McConaughy near Ogallala (30,000 acres when farm ponds. Thus, many quality trout fishing areas lack full), Lewis & Clark Reservoir on the South Dakota public access and require permission from landowners border (30,000 acres when full), and Harland County to enter. Reservoir in south-central Nebraska (13,500 acres when full) are the largest reservoirs in the state (Figure 2c). More than 100 species of fish live in Nebraska, In addition, smaller irrigation reservoirs in western and almost all of which can be identified with the Nebraska central Nebraska and flood-control reservoirs in eastern Game and Parks Commission’s superb online and Nebraska provide excellent fishing opportunities, as do interactive Fish Identification Guide. many farm ponds and sand pits across the state. Nebraska also boasts over 1,300 natural lakes, most of them The Commission operates four fish hatcheries in the Sandhills in north-central Nebraska; however, and one coldwater rearing station that produce warm- many of these are surrounded by private land without , cool-, and coldwater fish species for stocking in regular public access (Nebraska Wildlife Federation: various sections of the state. There are no National Fish http://www.nebraskawildlife.org/). Nebraska anglers Hatcheries in Nebraska. Warm- and coolwater species also fish a range of small streams in the northern and commonly requested by regional managers include westerns parts of the state, as well as major rivers northern pike, muskellunge (Esox masquinongy), including portions of the Missouri, Niobrara, Platte, and musky (northern pike x muskellunge hybrid), walleye, Republican rivers. , bluegill, channel catfish, white bass, crappie, bluegill x Lepomis ( cyanellus) While larger man-made waters, such as Lake hybrids, redear sunfish, and yellow (Perca Ogallala and the Sutherland Supply Canal, provide flavescens); all of these are stocked as fingerlings, blue-ribbon rainbow trout fisheries, most of Nebraska’s advanced fingerlings, or sub-adults. Hybrid species trout-supporting habitats flow through private land such as wiper (striped bass x white bass) are also in the northern and western parts of the state. Private popular with anglers who enjoy the aggressiveness and waters include, but are not limited to, flowing waters sport the hybrids provide. In 2005, Nebraska hatcheries (excluding the ), private natural lakes, produced almost 6.9 million fish, including roughly

Figure 2c. National Forests and Grasslands of Nebraska. From: http://www.roadless.fs.fed.us/states/ne/state3.shtml. 12 13 304,000 rainbow trout and 12,500 brown trout (U.S. and restoring trout habitats as well as in performing fish Fish and Wildlife Service 2005). The remaining species community assessments and private waters stocking and hybrids produced were black crappie (Pomoxis programs. Furthermore, across the state, the NGPC has nigromaculatus), blue catfish Ictalurus ( furcatus), 1) improved aquatic habitat through an Aquatic Habitat bluegill, channel catfish, grass carp, hybrid striped Program funded in part by a state Aquatic Habitat bass (wiper), largemouth bass, muskellunge, northern Stamp, 2) been active in aquatic education programs, pike, pallid sturgeon, ( rupestris), and 3) developed a Master Angler program that includes sauger, walleye, white bass, and . a special award for catch-and-release fishing. State size records are maintained for a wide array of species and Although relatively few are produced in state hybrids, and in many cases, information is provided for hatcheries, rainbow trout are popular in Nebraska, previous as well as present records. The rainbow trout and the NGPC stocks and manages coldwater trout state record was harvested by Frank Aloy in 1975 on a fisheries throughout the state. Most trout are stocked nightcrawler bait; it weighed 14 lb. 2 oz. as catchables (9 to 11 inches) and are placed in rivers, streams, and lakes to provide angling for both rural and Region 2 of the USFS manages three areas within urban fishing programs. The NGPC currently stocks South Dakota: the Black Hills National Forest and rainbow trout at two popular put-and-take recreation the Buffalo Gap and Fort Pierre national grasslands. areas (Two Rivers State Recreation site and Lake The Custer National Forest and Grand River National Ogallala), as well as in Panhandle ponds and pits. The Grasslands are administered by Region 1 of the Forest daily bag and possession limits for trout (all species) are Service. The South Dakota Game and Fish Department seven and 14, respectively. (SDGFD) has primary responsibility for managing the state’s fish resources. While some quality trout fishing areas in Nebraska offer public access, many are private waters South Dakota encompasses over 700,000 acres of and can be accessed only through private waters public fishing waters, including 450 public fishing lakes management (www.ngpc.state.ne.us). The NGPC does and 10,000 miles of streams and rivers managed for provide assistance for private landowners in developing (Figure 2d). Eight major tributary

Figure 2d. National Forests and Grasslands of South Dakota. From: http://www.roadless.fs.fed.us/states/sd/state3.shtml. 12 13 rivers (the largest include the Cheyenne, Missouri, chinook salmon, and rainbow trout while once again James, and White rivers) and the Missouri River provide walleye dominated (98.7 percent) all stocked fish. abundant fishing opportunities, as do the smaller streams from the Black Hills in the west to the Prairie Coteau Clearly, rainbow trout have only regional in the east. In the western third of the state, the Black importance in a state known for its diverse warmwater Hills offer 14 mountain lakes and more than 400 miles fisheries. Nonetheless, carefully crafted regulations of streams containing brook, brown, and rainbow trout. governing the take of trout, salmon, and their relatives On the surrounding prairie, reservoirs and more than (e.g., splake, whitefish, lake ) differ from place 50,000 stock ponds (many on private land) also provide to place. For example, on the Missouri River, the daily angling opportunity for largemouth bass, northern pike, bag and possession limits are five and 10, respectively; and a variety of panfish. Most fishing is concentrated in in Nebraska-South Dakota border waters, these limits Missouri River impoundments in the middle of the state are seven and seven; on western rivers, five and 10; and away from major population centers. Four massive and in the Black Hills, five and 10. In the Black Hills dams on the Missouri River have created more than 900 Trout Management Area, only one 14” or longer square miles of open water, 3,000 miles of shoreline, trout may be included in the daily creel, the SDGFD and a world-class freshwater fishery. Prairie stock ponds prohibits highgrading of any trout species, and several ranging from 1 to 100 acres also dot the central part specific locations are only, with of South Dakota. More than 120 glacial lakes ranging gear restricted to artificial lures only. South Dakota in size from several acres to more than 17,000 acres maintains state records for 62 species and hybrids. occur in the northeastern part of the state. Southeastern The state record rainbow trout was taken on July 4, South Dakota has more than 175 fishing lakes ranging 1980 from the Lake Oahe tailwaters by Tom Moore; it in size from 3 to 29,000 acres; some of these are glacial weighed 19 lbs. 4 oz. lakes while many are manmade lakes constructed for water conservation and irrigation. Three major rivers Wyoming fishing opportunities on National course through the southeastern region as well: the Big Forest System lands in Region 2 span 5,365,500 Sioux River, the James River, and the Missouri River, acres of the Bighorn, Medicine Bow-Routt [also see which includes Lewis and Clark Lake, a 30-mile-long Colorado, above], Shoshone, and portions of the Black Missouri River reservoir. Hills national forests and the Thunder Basin National Grassland (USDA 2006) (Figure 2e). The Ashley, The SDGFD lists 108 species of fishes (in 23 Caribou-Targhee, Bridger-Teton, and Wasatch-Cache families) as occupants of South Dakota waters; 36 of national forests are administered by Region 4 of the these are listed as rare and thus of special concern. Forest Service. These areas provide excellent angling As support for its programs, the Department operates opportunities in a range of aquatic systems, including four fish hatcheries, one of them primarily a salmon rivers, streams, alpine lakes, and reservoirs. Additional (especially chinook) spawning and imprinting opportunities exist throughout the state. Major station. The USFWS also operates a National Fish waterways include the Bighorn, Green, Belle Fourche, Hatchery in the state where fish are reared for use in Powder, and North Platte rivers. the Missouri River system. In 2005, state and Federal hatcheries produced more than 56 million fish (U.S. The Forest Service primarily manages aquatic Fish and Wildlife Service 2005). Slightly less than habitat, while the Wyoming Game and Fish Department 666,000 of these were coldwater species and hybrids, is responsible for managing fish populations on National dominantly rainbow trout and fall chinook salmon, Forest lands. The Wyoming Game and Fish Department but also including brown trout, lake trout, and splake. provides quality fishing opportunities to the public, The remaining warm- and coolwater fishes included improves aquatic habitat for game and non-game fishes, black crappie, bluegill, largemouth bass, muskellunge, and seeks to restore historic populations of native fishes. paddlefish, pallid sturgeon, smallmouth bass, walleye Management information and regulations (Wyoming and yellow perch, and 54 million (96.7 percent) of these Game and Fish Commission 2008a) are provided for were walleye! Two years later, in 2007, South Dakota five drainage areas in Wyoming: stocked almost 51 million fish. Lake trout, muskellunge, pallid sturgeon, and splake were no longer raised, and v Area 1: , , Greys River, black bullhead, brook trout, fathead , northern Hoback River, Gros Ventre River and Buffalo pike, and redear sunfish had been added. Coldwater fish Fork River Drainages and all drainages west were represented by 379,000 brook trout, brown trout, of the Teton and Snake River Ranges.

14 15 Figure 2e. National Forests and Grasslands of Wyoming. From: http://www.roadless.fs.fed.us/states/wy/state3.shtml.

v Area 2: Wind River, Bighorn River, Shoshone regulations and where she/he may be in what is often River, Clarks Fork and wild country. Drainages. The array of fishes identified as and v Area 3: the Niobrara River, Cheyenne River, for which creel limits are established reflects the Stockade-Beaver Creek, Sand Creek, Belle diversity of aquatic habitats encountered in Wyoming: Fourche River, Little Missouri River, Little largemouth, smallmouth, and rock bass (Micropterus, Powder River, Powder River, Tongue River, Ambloplites); bluegill, pumpkinseed, green sunfish, and Little Bighorn River Drainages. green sunfish-bluegill hybrid (Lepomis); crappie (Pomoxis); walleye and sauger (Sander); yellow v Area 4: Green River, Little Snake River, Bear perch (Perca); salmonids (including brook trout, River and Great Divide Basin Drainages. brown trout, cutthroat trout, golden trout, lake trout, rainbow trout, salmon, splake, , other trout v Area 5: North , Sweetwater River hybrids; Salmo, Oncorhynchus, Salvelinus); whitefish and Drainages. (); grayling (Thymallus); northern pike and tiger musky (Esox); catfish, bullheads, stonecats Although general regulations exist for segments of (Ameiurus, Ictalurus, Noturus, Pylodictis); ling/ all these areas, there are many clearly-stated exceptions (Lota); shovelnose sturgeon (Scaphirhynchus); and, for segments of these various drainages, reflecting freshwater drum (Aplodinotus). In 2005, Wyoming’s considerable care in managing local conditions. Such public hatcheries produced 4.9 million fish (U.S. Fish detail relies heavily on the angler to know both local and Wildlife Service 2005). Trout, kokanee, splake 14 15 and grayling constituted 3.8 million (78 percent) of Biology and Ecology that total, roughly 2 million of which were rainbow trout. Largemouth bass, northern pike, and walleye Systematics contributed less than 1.1 million of the total, and these were dominated by walleye (847,100). The vast majority Many names have been applied to rainbow trout of rainbow trout (almost 1.6 million) were produced for since they were first described in 1792 (Table 2). The fingerling stocking, reflecting the state’s long-standing short history of this nomenclature provided here should move toward put-grow-take fisheries and establishment serve management personnel in at least two ways. First, of self-sustaining populations (Wiley 2003a). it should reduce confusion over the recent dynamics in the trout’s scientific name and demonstrate how Historically, many of Wyoming’s high mountain taxonomists work to have names indicate evolutionary lakes were fishless due to isolation from lowland relationships. Second, it will help newcomers to the field streams as a result of uplifting and glacial activity that find important information about the species published formed these lakes (Wiley 2003b). Many high elevation under different names (especially Salmo gairderi). lakes provide coldwater fish habitat and have been or are stocked and managed by the WGFD. The rainbow trout (Oncorhynchus mykiss) belongs to the Class , Salmoniformes, and In 1999, theWGFD, after an extensive review Family Salmonidae (including trout, salmon, char, process (described in Annear et al. 1999), shifted whitefish, grayling). The earliest salmonid, to a coldwater stream fishery ranking system based driftwoodensis, dates from roughly 50 million on quantifiable and readily available data from one years ago and was described in 1977 from beds relying on the highly subjective variables of aesthetics, in (Wilson and Li 1999). Within the accessibility, and productivity (Table 1). The revised family, the genera Salmo and Oncorhynchus diverged system, based on estimated pounds of game fish per from a common ancestor during the 15 to 20 mile, ranks coldwater streams as blue-, red-, yellow-, million years ago (mya), with Oncorhynchus in the and green-ribbon fisheries (in declining order of fish North Pacific and Salmo in the North Atlantic density), is far more informative and easier for the Ocean. Toward the end of the Miocene (ca. 5 mya), angle to understand than the implications or basis of the Oncorhynchus evolved both salmon-like and trout- previous system. like species, with the latter giving rise to cutthroat and rainbow (or redband) lineages toward the end of In general, the creel limit in Wyoming for “trout the (ca. 2 mya). from the ice ages “ (combination of brown trout, cutthroat trout, grayling, and interglacial periods of the later Pliocene through golden trout, lake trout, rainbow trout, salmon, splake, the (2.5 million to 10,000 years ago) tiger trout, and other trout hybrids) is 6, no more than record members of the rainbow trout lineage as far one of which exceeds 20 inches. An exception is made south as southwestern (Behnke and Tomelleri for brook trout, for which the limit is 16, no more than 2002, Hendrickson et al. 2002). Of more immediate six of which exceed 8 inches. The Wyoming rainbow interest, however, and indicative of the incredible trout state record was harvested by Frank Favazzo in ecological flexibility of fishes in the rainbow trout 1969 in Burnt Lake, Sublette County; it weighed 23 lbs. lineage, are the recent discovery and rediscovery of and was 35-1⁄2 inches long. several poorly known trout taxa in mountain drainages

Table 1. Wyoming Game and Fish state-wide trout stream classification system. (Annear et al. 1999) Category Percent of Stream Miles Pounds of Sport Fish per Mile Blue Ribbon 2.3 ≥ 900 Red Ribbon 4.8 ≥ 500 and < 900 Yellow Ribbon 46.1 ≥ 100 and < 500 Green Ribbon 46.8 ≥ 1and < 100 Orange Ribbon unknown Any cool/warm water game fish present

16 17 Table 2. Scientific nomenclature for rainbow trout. (Modified from FishBase, 2006.) Salmo mykiss Walbaum, 1792 original combination Onchorynchus mykiss (Walbaum, 1792) present valid name Onchorrhychus mykiss (Walbaum, 1792) misspelling Oncorhynchus myskis (Walbaum, 1792) misspelling Parasalmo mykiss (Walbaum, 1792) new combination Salmo penshinensis Pallas, 1814 junior Salmo purpuratus Pallas, 1814 junior synonym Parasalmo penshinensis (Pallas, 1814) junior synonym Salmo gairdneri Richardson, 1836 junior synonym Salmo gairdnerii Richardson, 1836 junior synonym Salmo gairdnerii gairdnerii Richardson, 1836 junior synonym Fario gairdneri (Richardson, 1836) junior synonym Oncorhynchus gairdnerii (Richardson, 1836) other Salmo rivularis Ayres, 1855 junior synonym Salmo gairdneri irideus Gibbons, 1855 junior synonym Salmo gairdnerii irideus Gibbons, 1855 junior synonym Salmo iridea Gibbons, 1855 junior synonym Salmo irideus Gibbons, 1855 junior synonym Trutta iridea (Gibbons, 1855) junior synonym Salmo truncatus Suckley, 1859 junior synonym Salmo masoni Suckley, 1860 junior synonym Salmo (Jordan, 1892) junior synonym Salmo rivularis kamloops (Jordan, 1892) junior synonym Oncorhynchus kamloops Jordan, 1892 junior synonym Salmo gairdneri shasta Jordan, 1894 junior synonym Salmo gilberti Jordan, 1894 junior synonym Oncorhynchus mykiss nelsoni Evermann, 1908 junior synonym Salmo nelsoni Evermann, 1908 junior synonym Salmo irideus argentatus Bajkov, 1927 junior synonym Salmo kamloops whitehousei Dymond, 1931 junior synonym The species was initially described in Salmo, a erected by Linnaeus for the Atlantic salmon. Subsequent names reflect the best estimates of relationships at the time. When authorities are given in parentheses, it indicates that the species was previously described by that author but with a different name.

of northwestern Mexico (states of Chihuahua, Sonora, To understand the history of scientific names Durango, Sinaloa; see http://www.utexas.edu/tmm/ applied to rainbow trout, one must turn to the “Law tnhc/fish/research/truchas_mexicanas/ and http:// of Priority” established in the International Code of www.americanfishes.com/mexico/). Zoological Nomenclature (International Commission on Zoological Nomenclature 1999). With rare exception, The genus Oncorhynchus includes 10 or 11 this means that the earliest becomes the species and about 30 subspecies worldwide (Nelson accepted name. 2006). The name was first applied by Suckley in 1860 to the males (only) of (O. gorbuscha), Salmo, erected by Linnaeus in 1758 for the which was originally described as Salmo gorbuscha Atlantic salmon, was the first valid name in the Family by Walbaum (1792). Oncorhynchus was, therefore, the Salmonidae. The rainbow trout was originally named earliest applicable genus when biologists recognized the S. mykiss by Walbaum in 1792 from fish captured on distinct nature of Pacific salmon. the of Siberia (Behnke 1992). 16 17 Richardson subsequently applied the name S. gairdneri dorsal, adipose, and caudal (tail) fins, and a band of to steelhead (sea-run rainbow trout) collected from the pink to red along the sides. The back is often dark at in 1836 (McPhail blue to brown, the lower sides and belly silvery white and Lindsey 1970, Moyle 2002), considering them to to light yellow. Coloration varies with habitat, size, be different from the Kamchatka fish. In 1855, Gibbons and sexual condition. Stream residents and spawners described juvenile steelhead from a tributary of San tend to be darker, with more intense colors, while lake Francisco Bay as S. irideus. Because S. gairdneri had residents tend to be lighter, brighter, and more silvery. priority, S. irideus became invalid (a “junior synonym”) Juveniles often exhibit 5 to 13 dark, oval “parr marks” as a species name; it is, however, retained in the common along the side and light tips to dorsal and anal fins. The name (irid-, G., rainbow) and as a subspecies name for fins (except the adipose) are supported by segmented, Coastal rainbow trout (Oncorhynchus mykiss irideus). branched soft rays (no true spines); specific fin ray Subspecies represent geographic variants that exhibit counts include: dorsal 10 to 12, caudal (tail) 19, anal 8 somewhat distinct characteristics from other members to 12, pelvic 9 to 10, and pectoral 11 to 17. Scales are of a species elsewhere, yet do not warrant elevation to small and easily removed, with 110 to 160 pored scales full species status. along the , 18 to 35 scale rows above the lateral line, and 14 to 29 rows below it. There are 9 to Similarities in morphology and life history 13 branchiostegal rays. characteristics between the western rainbow trout and the brown trout and Atlantic salmon of the Salmonid life history characteristics eastern United States and led to retention of Richardson’s name until 1989, when anatomical Conservation and management practices for and molecular studies demonstrated closer affinities salmonids must consider the complexity of life between rainbow trout and Pacific salmon (genus histories characteristic of these fishes, particularly when Oncorhynchus; Behnke and Tomilleri 2002) than with maintenance of self-sustaining populations is desired. the eastern species of Salmo. Similarly, recognition The reason for such concern is simply that distinct life that the Kamchatka trout and western North American history stages must be considered as distinct ecological rainbow trout, now more correctly included within the entities, each with its own habitat requirements, genus Oncorhynchus, did not warrant separate species capabilities, tolerances, and ecological pressures. status led to the reapplication of the law of priority and Failure to ensure availability of stage-specific habitats return to the earliest available species name (mykiss) and reduces the likelihood that self-sustaining populations the emergence of the new combination, Oncorhynchus may be established or maintained. mykiss, as the valid name for rainbow trout. The life history stages of naturally reproducing Species description trout and salmon, including rainbow trout, with definitions and general comments about their Salmonids can generally be distinguished by the environments and characteristics, include: presence of a fusiform body, forked tail, adipose fin (a fleshy fin without internal supports along the midline of Egg – laid in depressions (redds) dug in spawning the back between and tail), and an enlarged gravels by females; potentially susceptible to fleshy or scaly process (axillary scale or process) at the predation by interstitial ; normal base of each (Moyle 2002, Nelson 2006). development requires free percolation of water The closely related smelts (Osmeridae) also possess an through the surrounding gravel, or at least adipose fin but lack the axillary process, while North relatively high humidity (exposure of in American (Ictaluridae) possess an adipose fin redds did not greatly reduce viability or otherwise but lack scales and have distinct barbels on the chin. affect development of chinook salmon and steelhead eggs, provided temperatures were The body of a rainbow trout is usually elongate, moderate and the substrate retained a moisture becoming somewhat deeper and compressed in larger content of at least 4 percent (Reiser and White fish (Moyle 2002, Nelson 2006). The mouth is large 1983]); fertilization to hatching time varies with and terminal, with the upper jaw usually extending to water temperature but is about 370 degree days or beyond the rear margin of the eye. Teeth are borne (ca. 100 days at 3.9 °C and 21 days at 14.4 °C on upper and lower jaws, vomer, palatines, and tongue. [FAO Fisheries and Department, Adult rainbow trout tend to be silvery in background rainbow trout fact sheet]). color, with black spots on the back as well as on the 18 19 Alevin/sac-fry – hatchlings usually remain in along sides of stream reaches or in eddies, but the gravels two to four weeks depending on frequently move into shallow, slow-moving water temperature (Raleigh et al. 1984, FAO Fisheries at night; feed primarily on aquatic invertebrates and Aquaculture Department, rainbow trout and allochthonous drift; susceptible to a variety of fact sheet) and rely on yolk for nutrition; highly predators and competitors depending on habitat; susceptible to exposure, probably a result of very different species of salmonids may exhibit parr high surface/volume ratio, simple epithelium characteristics for one to several years, and and lack of scales (exposure with associated parr marks may be retained by adults in small desiccation causes high mortality among sac streams; “fingerling” is often used by managers fry (Reiser and White 1983, Montgomery and and culturists concerned more with size than color Tinning unpublished]); susceptible to attack by patterns; in many salmonids, male fish of this interstitial invertebrates, fungi, microbes, etc.; age/size may mature sexually and use “sneak” transition from this stage to the next involves tactics to with adult females (this pattern critical events, including movement of the young is best known in Atlantic salmon (Salmo salar), fish to the surface through interstitial spaces chinook salmon, and some other salmon species among the gravels, “swim-up” to gulp surface [Montgomery et al. 1987]), but also occurs air and initially fill the gas bladder, movement to in steelhead and perhaps other rainbow trout slow-moving water near shore, and initiation of stocks (Schmidt and House 1979) and may have exogenous feeding. significance for reproductive biology of naturally spawning populations in Region 2. Fry – post-emergence, free-swimming, free-feeding stage; feed primarily on small Smolt – juvenile steelhead or salmon moving invertebrates; generally occupy shallow, warm, or preparing to move downstream to the sea; still or low velocity waters near shore where transition usually accompanied by increased they establish and defend territories (reviewed silvering of the body with near-obliteration of in Gerking 1994); variously mottled color previous colors and parr marks, enlargement of patterns; susceptible to a variety of terrestrial pectoral and other fins, and increased forking of the and aquatic predators as well as competition tail; entry into sea water involves changes in ion from both salmonid and non-salmonid fishes exchange pumps in and other physiological (e.g., Hayes 1989; Gaudreault et al.1986 adjustments; some rainbow trout in lakes and described between juvenile brook reservoirs lack a physiological smolt stage, but charr [Salvelinus fontinalis], and adult ninespine exhibit movements and life history similar to sticklebacks [Pungitius pungitius]); tendencies steelhead. (e.g., juvenile rainbow trout migrate to move from cover at night may increase from natal streams to lake or reservoir, instead of exposure to predators and stronger currents (see ocean, for rearing [Raleigh et al. 1984]). Fausch et al. 2001 regarding rainbow trout fry displacement in current; increases of as little as Adult – reproductive or potentially reproductive 4 to 14 cm per sec in water velocity displaced fish; occupy wider ranges of stream or lake brown trout fry downstream at night [Heggenes habitats than fry or parr; feed on aquatic 1988, Heggenes and Traaen 1988]); in streams, invertebrates, drift, and occasionally small fish; fry prefer shallower water and lower velocities like parr and fingerlings, are susceptible to a than do other life stages of stream-dwelling trout; variety of predators and competitors depending once fry move from natal gravels to rearing areas, on habitat, size, etc. they tend to exhibit three distinct genetically influenced movement patterns: downstream Distribution and abundance movement to a larger river, lake or to the ocean; upstream movement from an outlet river to a lake; All populations of rainbow trout in Region 2 local dispersal from natal spawning grounds to have been established through stocking of fish from rearing areas (Raleigh et al. 1984). their native range (Figure 3) or from hatchery stocks whose origins trace to taken from the native Parr/juvenile/fingerling – sexually immature range. The native range of Oncorhynchus mykiss individuals larger than fry, usually with parr includes cool waters of the , from northern marks (dark, oval marks) along their sides; occupy Baja California to eastern as far south as the Amur and defend feeding territories in moving water River and Island, although these southern 18 19 Figure 3. Native distribution of rainbow trout in the United States. Green – current distribution, red, historic distribution NatureServe 2006. records may be due to straying by steelhead (the and Middle Columbia River are Threatened. Even the sea-run form of rainbow trout) from well-established McCloud River redband trout, the fish from which Kamchatka Peninsula populations (Fishbase 2006). In most modern hatchery stocks have been derived, is a , rainbow trout are native to Pacific coast candidate for listing under the Act. streams from the Kuskokwim River, , south to northern Baja California, upper In stark contrast to the declines of many native drainage (Arctic basin), , and British Columbia, rainbow trout stocks is the continuing expansion of and endorheic basins of southern (Table 3; Page their range by introductions throughout the world; this and Burr 1991). may be regarded as global in its present distribution (Fishbase 2006). As noted elsewhere in this assessment, Population trends (local, regional, and rainbow trout, particularly derivatives of the McCloud rangewide) River redband trout from California (Hedgpeth 1991), have been reared in hatcheries since the middle of the The range and population sizes of rainbow trout 19th century. Fish from those hatcheries have been are declining in various parts of their native range while distributed into coolwater systems in North America expanding in other areas due to stocking (NatureServe (Figure 4), , Europe, Asia, Africa, and 2006). For example, within their native range, steelhead , as well as a number of smaller, non-continental populations from Southern California and the Upper land masses (e.g., ; MacCrimmon 1971). Columbia River are listed as Endangered, while those In Canada, the rainbow trout occur outside British from the Central and South-Central California Coast, Columbia from the Avalon Peninsula of Newfoundland, Snake River Basin, Lower Columbia River, California across the southern portions of the provinces from Nova Central Valley, Upper (winter run), Scotia to , north to central , to northern

20 21 Table 3. Original ranges and subspecies considered within Oncorhynchus mykiss. Rainbow trout of coastal basins Kamchatkan rainbow trout Oncorhynchus mykiss mykiss* Coastal rainbow trout Oncorhynchus mykiss irideu*

Rainbow trout of the mid- and upper Columbia and basins Columbia River redband trout Oncorhynchus mykiss gairdneri*

Redband trout native to six internal basins of the Northern , plus the basin Redband trout of the Northern Great Basin Oncorhynchus mykiss newberrii

Redband trout of the northern basin Sacramento redband trout Oncorhynchus mykiss stonei

Three subspecies of trout native to the basin California golden trout Oncorhynchus mykiss aquabonita Kern and Oncorhynchus mykiss gilberti Upper Klamath redband trout Oncorhynchus mykiss newberii

Rainbow-like trout native to Baja California and the Rio Yaqui, Rio San Lorenzo, and Rio del Presidio drainages of Mexico (tributaries to the Gulf of California). Baja California rainbow trout Oncorhynchus mykiss nelsoni *taxa that include sea-run (anadromous) trout. The term steelhead is often applied to anadromous forms of Oncorhynchus mykiss, but is not endorsed by Nelson, et al. 2004. (From Behnke 1992, 2002)

Alberta, and in the . No other coolwater sport and insufficient sampling of wide-ranging individuals. Fish food fish has experienced such a purposeful expansion exhibit both types of behavior (Mellina et al. 2005), of range. with the importance and timing of environmental cues as well as the genetic influences (Behnke 1992) in Activity patterns promoting movement varying from stream to stream. Thus, both sedentary and movement types of behavior Much is known about the activity patterns of are likely to be found within any given population, wild, self-reproducing, and introduced rainbow trout. although the frequency of these behaviors varies Some aspects of their behavior are described in greater considerably among streams and among individual fish detail elsewhere in this assessment (e.g., sections on as they alter their responses to changing conditions. In feeding, reproduction). Here we focus on movements, British Columbia, for example, movement by stream- particularly of adults, at various scales. dwelling trout was stimulated by decreases in dissolved levels and/or by increases in sedimentation Rainbow trout are primarily diurnally active, with during road construction (Mellina et al. 2005). feeding peaks normally during crepuscular periods. During the day, they tend to remain within a confined An additional pattern of movement common to area of a stream or lake, but may move from areas of rainbow trout and many other species of salmonids low to high food density or from rapidly flowing water (e.g., Pacific and Atlantic salmon, brook trout, brown with higher food supply to resting areas with reduced trout, Arctic charr) is migration to and from , flow. Because of such behavior, stream-dwelling trout lakes, or other distant locations in streams. Such have often been considered to be sedentary and to have migrations may take fish to richer feeding areas in relatively small home ranges (Mellina et al. 2005, Rio oceans or lakes or to areas with more suitable or Grande SCP 2005). However; recent studies demonstrate abundant spawning substrates. Rainbow trout that that long range movements are common in stream- undertake such migrations to the sea have been termed dwelling trout and that experimental and observational steelhead, and genetically based differences in behavior bias have favored recording of sedentary behavior, with of anadromous and stream-dwelling trout have enabled 20 21 Figure 4. Distribution and conservation status of rainbow trout in the United States. NatureServe 2006. both lineages to coexist without hybridizing (Behnke or more well separated habitats, and a large fraction of 1992). , coastal rainbow trout, the population participates (Mellina et al. 2005). inland redband trout (rainbow trout), and rainbow trout coexist by maintaining reproductive isolation by Migrations are initiated by spatial changes choosing different preferred habitats throughout all in stream or lake conditions as well as by seasonal life stages (Behnke and Tomelleri 2002). The longest effects on behavior of fish. For example, in Nebraska, known spawning migrations by native steelhead trout nonnative rainbow trout of Lake McConaughy migrate returning to their natal grounds to spawn extended from 145 km or more upstream in the to the almost 1,600 km from the sea to the upper Columbia suitable tributaries for spawning (Behnke and Kloppel River, British Columbia, and to the upper Snake River 1975, Behnke 1992). In spring, a relatively large near Twin Falls, . Both these runs have been largely lakeward migration is followed by a period of restricted blocked by dams, with accompanying major declines or movements throughout the summer and autumn, extirpation of native sea-run fish and an apparent loss of followed by movements to overwintering habitats. genetic variation once present in such fish. Adults are not the only life history stage to move. Because native stream-dwelling trout, like most Increased temperatures in spring will initiate movements other non-anadromous trout, generally lack a strong by juveniles from streams to lakes. Lentic habitats often hereditary basis for directed movement (Behnke 1992), provide greater thermal stability and abundant food and migrations of landlocked fish between streams and lakes habitat resources needed for growth and survival. In the are often attributed to fish stocked from populations summer months, trout primarily focus on feeding, and derived from steelhead. In such populations, long-range this behavior determines their distribution in streams movement occurs regularly, is directional between two and lakes; in the winter, fish focus on overwintering in larger, deeper areas (Mellina et al. 2005). 22 23 Hatchery (catchable and subcatchable) fish may Rainbow trout are typically spring spawners, but also influence movements of wild trout in streams. spawning time differs in various locations, elevations, Stocking densities and rates of removal of hatchery and among different hatchery-reared and various hybrid trout by anglers will influence wild and stocked trout strains. Several factors are addressed separately in the movements. The effects of hatchery fish on wild trout following descriptions of suitable habitat for various populations is of special importance to managers life stages, but the reader should keep in mind that (Behnke and Tomelleri 2002) because while stocked fish must respond to the combined effects of multiple fish compete for all the same resources as do wild physical, chemical, and biological variables in their trout, they can have lower reproductive success in respective environments. In self-sustaining populations, nature and then be lost from the gene pool in as little as fish encounter all the important factors in a suitable, two generations (Skaala et al. 1990). Artificial density but usually not optimum, range of conditions capable created by stocking should be neither high nor long of supporting each life history stage. The combination lasting to minimize stress and/or displacement of wild of factors should be of particular interest to managers trout populations (Behnke 1992). since the mix sets the carrying capacity for that stream, and that capacity can be altered if one or more of the Habitat factors is altered (Bjornn and Reiser 1991).

Rainbow trout pass through several distinct life Spawning habitat history stages (egg, alevin or sac fry, free-swimming fry, juvenile, adult), each with its own habitat requirements. Spawning success is directly related to water Insufficiency or absence of habitat for any of the early quantity and quality, substrate composition, area of life history stages will obviously depress recruitment suitable substrate, and cover (Table 4). The number into later stages. of spawning sites directly relates to the availability of suitable habitat. The amount of suitable stream Four general types of required habitat may substrate for spawning tends to increase with stream be linked to the various stages of trout life history: order (Bjornn and Reiser 1991). spawning habitat, nursery or rearing habitat (including egg incubation, fry, and juvenile habitats), adult Streamflow: Streamflow regulates the amount habitat, and overwintering habitat (Behnke 1992). of spawning area available and water over gravel For the purpose of this assessment and to better aid in beds. As the snow pack melts in the spring, rivers rise management decisions, trout habitat has been broken and inundate additional spawning habitat. Flows may down into the following six sections: continue to increase to the point that velocities become too high for spawning and scour (see below) ensues, v Spawning habitat such that high streamflow then outweighs the benefits of v Egg incubation habitat increased water levels. High waters can decrease stream v Fry habitat productivity, and thus relationships between flow and v Juvenile habitat suitable substrate become important tools for managers. v Adult habitat The USFWS developed an instream flow incremental v Overwinter habitat

Table 4. Spawning habitat for western trout and kokanee salmon. (Adapted from Reiser and Bjornn 1979, Schuett- Hames and Pleus 1996, Morris and Caverly 2004, and Larsen (no date).) Water depth Water velocity Substrate size Ave. Size of Recommended Area Per Species (m) (m/s) per (cm) Redd (m2) Spawning Pair (m2) Kokanee 0.061 0.2 - 0.7 small gravel* — — Steelhead 0.244 0.4 - 0.9 0.5 - 10.2 4.4 - 5.3 17.6 - 21.2 Rainbow 0.244 0.5 - 0.9 0.5 - 5.1 0.2 0.8 Cutthroat 0.061 0.1 - 0.7 0.5 - 10.2 0.1 - 0.9 0.5 - 4.5 Brown 0.244 0.2 - 0.6 0.5 - 7.6 0.5 2 Small-bodied salmonids** 0.1 moving 0.8 - 6.4 — 1 *Morris and Caverly 2004. **Schuett-Hames and Pleus 1996 – includes: resident rainbow, cutthroat , kokanee, brown, brook, and Dolly Varden.

22 23 methodology (IFIM) to estimate the amount of suitable spawning adults and to cover the redd when fry emerge habitat (Bjornn and Reiser 1991). (Workman et al. 2004).

Temperature: Rainbow trout are able to spawn Substrate: Rainbow trout are primarily stream in temperatures ranging from ~2 to 20.0 ºC (36 to 68 spawners and generally require tributary streams ºF; Raleigh et al. 1984, Bjornn and Reiser 1991), but with gravel substrates in areas for successful spawning is generally initiated when water temperature reproduction (Raleigh et al. 1984). The suitability of exceeds 6 to 7 ºC (42 to 44 ºF) regardless of geographic gravel substrate for spawning is directly related to area (Behnke 2002). In wild, self-sustaining rainbow fish size (Bjornn and Reiser 1991, Raleigh et al. 1984, trout populations, spawning is often triggered when the Workman et al. 2004). In general, substrate particles fish move from colder to warmer waters of river or lake must be large enough to enable successful alevin tributaries. Rainbow trout that spawn in lakes with inlet emergences from the redd (Workman et al. 2004). The and outlet streams may spawn as much as one month female generally selects a redd site in gravel substrates earlier in the outlet than the inlet due to temperature located at the head of a riffle or on the downstream edge differences (Raleigh et al. 1984). Spawning date and of a pool. The redd is constructed by the female and temperature vary considerably among hatchery strains is typically longer and deeper than her greatest body of rainbow trout, so managers can stock fish that spawn depth (Raleigh et al. 1984). During redd construction under sets of conditions that maximize the survival and spawning, streambed particles are displaced so that of the offspring. Artificial propagation has placed an fertilized eggs can be deposited in one or several “egg emphasis on developing fall spawners, thus enabling pockets.” Depths of egg pockets will vary according to hatcheries to produce size-specific rainbow trout year the size of the female and local substrate conditions, round (Behnke 2002). For example, spring-spawning but on average they range from ~0.08 m for small fish strains tend to spawn when water warms sufficiently to (characteristic of most stream spawners) to ~0.20 m for allow normal embryo development. Fall-spawning trout large individuals (e.g., the size of sea-run steelhead; must allow sufficient time for their embryos to reach a Schuett-Hames et al. 1996). Redd construction reduces critical stage of development before the water becomes the amounts of fine sediment and organic matter in too cold (Bjornn and Reiser 1991). the pockets where eggs are deposited. Once spawners deposit eggs and sperm, the females cover the eggs Space: Larger fish dig larger redds, and poor with hydraulically-displaced particles (Bjornn and quality or insufficient spawning habitat may force Reiser 1991). females to make several redds. The density of redds depends largely on the area of suitable habitat for Cover: Trout may arrive at spawning grounds spawning; the number, size and behavior of spawners; weeks or months before they are ready to spawn, so and the area required for each redd. The average area of sufficient cover creates an environment where fish a redd with a single egg pocket is ~0.2 m2. are less vulnerable to disturbance and predation for extended periods of time. Cover for rainbow trout Water depth and velocity: Females typically waiting to spawn may include, but is not limited to, choose spawning sites at water depths greater than 18 overhanging vegetation, undercut banks, submerged cm with greater than average velocities (e.g., 48 to 91 vegetation, submerged objects such as logs and rocks, cm per s). Velocities are measured at the upstream edge floating debris, deep water, and areas of turbulence and/ of the redd because that point is believed to most closely or high turbidity (Bjornn and Reiser 1991). approximate conditions before the redd was constructed and thus reflects the depth and velocity selected by Streams, tributaries, rivers, lakes, and the fish (Bjornn and Reiser 1991). Water velocity reservoirs: Rainbow trout spawn almost exclusively in is important for successful spawning because faster streams (Raleigh et al. 1984). Lakes and reservoirs with water delivers well-mixed and oxygenated water to the no inlet or outlet streams generally limit, and in most redd, and it must be fast enough to penetrate and move cases inhibit, reproducing populations of rainbow trout. through the interstices of the redd. Continuous flow of Rainbow trout in lakes and reservoirs with inlet and water through the egg pocket is critical for delivering outlet streams are thought to have similar life history sufficient oxygen to embryos, removing metabolic as steelhead (sea-run rainbow trout) without the smolt waste products, and keeping the substrate free from life stage. silt so fry can emerge from interstices (Raleigh et al. 1984, Workman et al. 2004). Water depth is important Trout production is typically most successful in because water must remain deep enough to support the streams with a pool-to-riffle ratio of approximately 1: 24 25 1. While trout habitually spawn in both permanent thus shorter incubation period and time to emergence and intermittent tributaries, the latter (including rivers (Raleigh et al. 1984). below dams whose discharge fluctuates drastically over short periods) tend to expose redds and either Water depth and velocity: Depth is not expected stress or kill eggs and especially alevins. Trout will to be a limiting factor for egg incubation as long as readily utilize intermittent streams if competition for the eggs are moist during incubation, and egg pockets redd sites is too high in permanent streams (Erman and are submerged from the time of hatching until the fry Hawthorne 1976). emerge (Raleigh et al. 1984).

Nursery habitats – egg incubation and fry Substrate: The redd environment is most rearing favorable right after construction and may change little or drastically depending on weather, streamflows, other The habitat requirements of embryos during spawning trout, and other fish in the area. Porosity is incubation are quite different than those of spawning highest right after the redd is constructed and declines adults because successful incubation and emergence of over time as the interstitial spaces acquire fine sediments fry depend on precise combinations of extragravel and (Bjornn and Reiser 1991). Normally, particles should intragravel chemical, physical, and hydraulic variables. be >1 cm in diameter to permit adequate percolation Dissolved oxygen, water temperature, biochemical for successful embryonic development (Raleigh et al. oxygen demand of material carried in the water and 1984). Egg densities in natural redds are typically lower deposited in the redd, substrate size, fine sediment, than those in artificial culture facilities (Bjornn and channel gradients, channel configuration, water depth, Reiser 1991). surface water discharge, velocity, porosity of gravel in the redd and surrounding streambed and the velocity of Cover: Cover is not thought to be a limiting the water through the redd are important variables that factor for egg incubation; in fact, spawning gravels determine incubation success and thus reproductive are more likely to occur away from quiet or slowly success (Bjornn and Reiser 1991). The period of egg flowing waters near shorelines where deposition of fine incubation begins at the end of spawning and normally sediments occurs (Raleigh et al. 1984). lasts 30 to 100 days, with the duration at a particular location largely dependent on temperature (Raleigh et Fry habitat al. 1984). Fry absorb most or all of the contents of their Streamflow: Above-substrate streamflow is yolk sac at a length of roughly 35 to 40 mm, 3 to 4 usually less significant during egg incubation than months after hatching. They then move through the percolation of water through the gravels surrounding interstices of gravels surrounding the egg pocket to egg pockets to provide oxygen and remove wastes. The the substrate surface and to shallow, low-velocity most significant exception to this occurs during seasonal (and usually relatively warm) water along the shore. spates associated with periods of rapid snowmelt Fry inhabit low velocity water and protective cover or heavy seasonal rains that can displace streambed typically found along the margins of streams and in gravels in the redd (see section on Scour below). spring seeps, side channels, backwaters, and small tributaries (Behnke 1992). Dissolved oxygen: Eggs are generally most vulnerable to hypoxic conditions during early stages For the purpose of this assessment, we recognize of development (Bjornn and Reiser 1991). Salmonids fry habitat as that occupied during the period from incubating at low dissolved oxygen levels are weak, emergence from spawning gravel to the time when small, and slower to develop and have an increased they become juveniles at approximately 4 months post- frequency of abnormalities. emergence (Raleigh et al. 1984).

Temperature: Incubation time and success varies Temperature: There appears to be almost no inversely with temperatures. Rainbow trout eggs can variation in the critical thermal maximum (temperature withstand temperature extremes of ~35 to 61 ºF (~1.6 at which animal loses control of normal orientation and to 16 ºC), but temperatures of 45 to 50 ºF (~7 to 10 swimming performance) for rainbow trout at sizes of ºC) yield the highest survival rates among embryos. ~4 to >30 cm (reviewed in Rodnick et al. 2004). During In general, the higher the temperature, within the summer periods, fry tend to occupy temperatures acceptable range, the faster the rate of development and averaging 13 to >19 ºC, depending on local conditions. 24 25 However, their shallow, near-shore habitats may place, thus few fry can be found more than 1 m from experience considerable short-term (daily) fluctuations cover. Types of cover include, but are not limited to, in temperature, as they are particularly susceptible aquatic vegetation, woody and other debris, and the to changes in air temperature, insolation, and other interstices between rocks. Raleigh et al. (1984) noted conditions that influence shallow, slow-moving waters. that coarse-grained substrate is used for cover. Growth rates during this phase, as during the subsequent juvenile phases when there are similarly no nutrient or Juvenile habitat energy expenditures for reproductive activity (Cunjak and Green 1986), are highly temperature dependent. While the size of juvenile rainbow trout may For example, (Raleigh et al. 1984) cites a growth rate vary depending on local conditions, here we include at 10 ºC that was ten times greater than at 3 ºC, values individuals that range in length from ~4 to 20 cm (~1.8 that indicate a Q10 of ~27, far greater than the Q10 values to 7.9”) or from ~4 months of age to sexual maturity of 2 to 3 recorded for most biological functions [Q10 (typically at age 2). Variables that factor into juvenile is a factor by which the rate of a biological function habitat preferences and use include substrate, cover, increases when the temperature is raised by ten depth, velocity, temperature, size, and activity of the 10/t2-t1 degrees C; it is calculated as Q10 = R2/R1 , where individual trout, intra- and interspecific interactions, t2 >t1]. This difference was likely exaggerated by a test season, and stream location (Raleigh et al. 1984). Thus, temperature near the lower limit of their tolerance; Q10 juveniles explore and occupy a wide range of habitats as values increased for metabolic rates of larger rainbow they grow and mature. trout as they neared their critical thermal maximum (Rodnick et al. 2004). Streamflow: As noted above, as fry grow and enter their juvenile stage, they move into deeper Water depth and velocity: Fry occupy shallower and more swiftly flowing water that offers greater water and lower velocities than stream rainbow trout of complexity of cover for larger fish and larger and more any subsequent life stage. Fry typically occupy depths diverse food supplies. There is a strong correlation ranging from 25 to 50 cm, and will utilize velocities between year class abundance and flow regimes, less than 30 cm per sec, but they prefer velocities less with a strong positive correlation between year class than 8 cm per sec. Fry are especially vulnerable to abundance and lower than normal flows (Behnke 1992). being washed away outside their preferred range of This probably reflects greater availability and stability velocities and survival decreases dramatically with of fry rearing habitat as much as availability of slower increased velocity. Predictably, fry are more apt to be water for juveniles moving into deeper habitat. swept away in the event of a flood (Behnke 1992). As the fish grow, they move into faster, deeper waters Temperature: Temperature preferences of (Raleigh et al. 1984). juveniles vary considerably, in part due to changes related to age and acclimation temperature (Raleigh et Substrate: Fry substrates typically range from al. 1984). As they grow, juveniles move into deeper and mud and silt to bedrock and cobble. Bustard and Narver swifter water more characteristic of that occupied by (1975) reported that fry substrate was most closely adults. In general, however, they should thrive at mean associated with particles ranging from 10 to 25 cm in summer temperatures in which adults thrive and grow diameter, but this will vary considerably depending on (~10 to 18 ºC). habitats available. As noted above, fry establish feeding territories that vary with size, population density, Water depth and velocity: Once rainbow trout visibility, and food density (Imre et al. 2004;, Keeley reach 12.5 to 15 cm, survival rates increase, and at this 2002, 2003); in an experimental system, Imre et al. stage, they will relocate to riffle areas where territories (2004) measured mean territories of approximately 80 are established in deeper waters such as pools (Behnke to 160 cm2, but others have suggested the range may be 1992). Velocity preferences of juvenile rainbow as great as 15 cm2 to 1 m2 (Brown 2003). Keeley (2003) trout vary widely as they are dependent partially demonstrated that population self-thinning (a decline on individual activity, whether the fish is stationary in population density apparently not due to predation (resting) or swimming (feeding, exploring). Other or other local deaths) occurred in young-of-the-year factors affecting velocity preferences in steelhead as they grew under constant food conditions. are season and flow. Juveniles occupy a wide range of depths depending on their activity and geographic Cover: After hatching and during the first months location (Raleigh et al. 1984). of life, cover is critical for successful rearing to take 26 27 Substrate: Undercut banks are used for physiological changes that may jeopardize their health. establishing territories, but juvenile rainbow trout For example, low dissolved oxygen can result in altered commonly associate with more exposed areas over swimming speed, a decline in growth rates, reduced gravel, cobble, and near boulders. When stationary, fecundity, and even constrain spawning. Temperature juveniles have demonstrated a preference for gravel and dissolved oxygen levels influence depth distribution over cobbles and boulders, and they encounter silt and of trout in various environments (Raleigh et al. 1984). sand during random swimming and when resting or foraging in side channels or nearshore habitats (Raleigh Space: The space required for individual et al. 1984). territories largely depends on the total suitable space available. The complexity of the habitat along with food Cover: A cover area of 15 percent of total stream availability and the presence of predators all determine area or greater is adequate for juveniles to avoid what part of the available suitable space fish use. As predators and to provide resting grounds (Raleigh wild trout age and and grow in size, the amount of space et al. 1984). Cover may be found instream or on the required for territorial needs increases. streamside. In the water, cover includes submerged vegetation, debris piles, woody debris, logs, boulders, Water depth and velocity: Stream trout typically and other objects that provide protection or alter live at depths of 0.3 m or greater and in areas where local current flow patterns. Streamside cover may be slow waters for resting are available. Fast waters are provided by overhanging vegetation, undercut banks, also used by adult rainbow trout because strong currents and other objects that hang over the water (Raleigh dislodge, suspend, and carry food. Trout often forage et al. 1984). When cover provides shade, it probably by holding station in eddies or other locations with also enhances visibility of exposed prey and reduces reduced current adjacent to swift water, moving into the the ability of predators to see the lurking juvenile swift current to intercept prey. Fish occupy a wide rage (Helfman 1981). of depths depending on their activity (e.g., resting vs. foraging; Raleigh et al. 1984). Adult habitat Substrate: Adult trout are less constrained to Rainbow trout are considered adults when they specific substrates than smaller life history stages. As reach sexual maturity at age 2 or 3 or when they indicated in other sections here, they range widely in attain lengths of ~20 cm (~8.0”), a size when many lakes, rivers and streams, and at various times in their are capable of maturing given the proper conditions adult lives, they can occupy all but the shallowest of (Raleigh et al. 1984). marginal habitats. Key components of river substrate for adults are large structure (e.g., boulders, woody debris) Streamflow: There is a direct relationship that diversifies local instream flow patterns to produce between annual streamflow and the quality and amount microhabitats differing in velocity and cover, and pools of available trout habitat. At low water levels, undercut and undercut banks that provide quiet refuges. banks, large portions of instream cover and desired shoreline habitats may be exposed, while at very high Cover: The addition of three-dimensional cover, water levels excellent habitats may be in deep water or present in both instream and streamside areas and inordinately strong currents (Behnke 1992). The most providing extra depth, preferred substrate, overhanging critical period is usually during base flow, the lowest vegetation, submerged vegetation, undercut banks, flows of late summer to winter. Base flows 50 percent instream objects (i.e. debris piles, woody debris, logs, or more of the average annual daily flow are ideal for large rocks), increases the complexity of the space maintaining quality trout habitat, while base flows of 25 available and thus the carrying capacity (Bjornn and to 50 percent are considered fair, and below 25 percent Reiser 1991, Behnke 1992, Raleigh et al. 1984) . A are considered poor (Raleigh et al. 1984). cover area of 25 percent of the total stream area or greater is suitable for adult rainbow trout. (Raleigh et Temperature: Summer temperatures of 10 to al. 1984). 18 ºC are optimal for stream-dwelling trout (Behnke 1992). As water temperatures increase, dissolved In streams, tributaries, rivers, lakes, and oxygen levels decrease, and this may be detrimental or reservoirs: Rainbow trout populations that successfully lethal to the fish if levels drop substantially. Rainbow reproduce in lakes with inlet and outlet streams typically trout can survive at suboptimal dissolved oxygen levels, spend two summers in a stream and two summers in a but not without a cost and subsequent behavioral or lake before they are considered mature (Raleigh et al. 26 27 1984). Pools provide resting areas and refuge from trout fry commonly overwinter in shallow areas of low adverse conditions and are thus inhabited throughout velocity near the stream margin. the year by adult and juvenile stream rainbow trout (Raleigh et al. 1984). Substrate and cover: Fry and small juveniles of rainbow trout and steelhead preferentially inhabit Overwinter habitat areas with coarse substrate (i.e., gravel, cobble, woody debris), tend to take refuge in the interstices of these The amount of adequate overwintering habitat is substrates during the day, and emerge into the water a major factor limiting salmonid densities, often more column at night where they may feed (Bustard and so than the amount of summer-rearing habitat. The key Narver 1975, Hillman et al. 1987, Simpkins 1997, features of winter habitat for juvenile salmonids appear Morgan and Hinojosa no date). In the interior of British to be substrate, cover, and lower water velocity. These Columbia, steelhead or rainbow trout occupied rock features are affected by natural processes, especially crevices or large substrata, often associated with riprap- those related to watershed characteristics such as stabilized banks (Swales et al. 1986). In streams with gradient, geology, and hydrologic regime, as well as large amounts of large woody debris, juvenile salmonids land use practices. experience higher overwinter survival than in streams with less (Murphy et al. 1984a in Morgan and Hinojosa Streamflow: The effect of stream discharge no date). If sufficient cover occurs locally, rainbow trout on winter habitat varies with geography. In contrast may not move downstream during or preceding winter to the , where heavy winter (Raleigh et al. 1984). rainfall generates spates with potential for scouring, sedimentation, and washout of fish (Morgan and Food habits Hinojosa no date), streams in the more arid Rocky Mountain Region are likely to experience low flow Rainbow trout are opportunistic feeders, and and greater threat to fish of stranding or formation of their primary food items depend in part on the anchor ice during winter. Mitro et al. (2003) found a stage of life history as well as the habitat occupied relatively tight correlation between abundance of age (Table 5). Although no comprehensive list of foods 0+ rainbow trout and river discharge in the second half ingested is attempted here, one can expect these of winter (15 Jan-31 Mar) in the Snake River, Idaho, fish to feed on items characteristic of the benthos possibly indicating greater availability of complex (organisms associated with the substrate or with streamside habitat at higher flows. other solid materials like woody debris), the water column (drift in streams and and nekton Temperature: Cooling of water as winter in lakes), and surface (animals that have fallen into approaches stimulates movements of trout to the water or are swimming). Fry restricted to quiet overwintering habitat. Such movements tend to be waters feed on small and other invertebrates, downstream to areas with greater winter flow, deeper including , amphipods, cladocerans, and pools, or more groundwater discharge (Morgan and many types of both terrestrial (e.g., adult Coleoptera, Hinojosa no date). Winter stream temperatures of Diptera, Formicidae, larval Lepidoptera) and aquatic greatest concern are, of course, those near, at, or insects (e.g., larvae and pupae of midges, black flies, occasionally below freezing (0 ºC, 32 ºF). Supercooling ; , craneflies, soldierflies, , (temperatures <0 ºC) in freshwaters can occur where stoneflies) (Fishbase 2006). water movements or other phenomena inhibit formation of surface ice cover. Under such conditions, ice can Diets of juvenile and adult trout are even more form on and in the substrate, freezing fry and juvenile diversified, with a wide assortment of terrestrial and fish, or it can form highly abrasive free-floating ice aquatic insects, other aquatic invertebrates including crystals (frazil ice; Simpkins et al. 2000). nematodes, leeches, , gastropod and other mollusks, and benthic and planktonic crustaceans Water depth and velocity: For adult fish, (cladocerans, isopods, amphipods, , crayfish), overwinter survival is directly related to the availability both small ray-finned fishes and brook lampreys, fish of deep water with low current velocity and protective eggs and larvae, detritus, benthic algae (Fishbase 2006), cover typically found in deep pools with large boulders and even an occasional lizard (Lintermans 1992), or deep beaver ponds (Behnke 1992). Stream resident mouse (Merz 2002), or bat (Y. Bernstein, personal

28 29 Table 5. Known foods of rainbow trout. (Lintermans 1992, Kerr and Lasenby 2000, Merz 2002, Fishbase 2006; Montgomery, Bernstein, William Leibfried, personal observations.) Algae Snails and other mollusks Cladophora benthic Fishes unidentified fish eggs and larvae Detritus American Nematodes Bloater chub Bluegill Leeches Brook Brook trout Annelids Brown bullhead Fathead minnow Aquatic insects Five spined stickleback dragonflies Green sunfish damselflies chironomid midges - larvae & pupae Largemouth bass simuliid black flies - larvae & pupae Longfin smelt rhyacophilid caddisflies - larvae & pupae Nine spined stickleback hydropsychid caddisflies - larvae dytiscid beetles Rainbow trout haliplid beetles Redside shiner dipteran craneflies dipteran soldierflies Sockeye salmon ephemeropteran (including baetid) mayflies Speckled dace plecopteran stoneflies Threadfin shad Three-spined stickleback Terrestrial insects Yellow perch adult Coleoptera Diptera Formicidae Southern water (Australia) larval Lepidoptera Mammals Aquatic crustaceans mouse amphipods (Gammarus) bat cladocerans isopods shrimps crayfish

observation). Detritus and benthic algae may reflect Clearly, rainbow trout are likely to feed on any incidental ingestion with animal prey, but trout may organisms of potential–or perceived–nutritional value. also derive meaningful nutrition from partial digestion Knowledge of trout feeding behavior and ecology will of these materials or epiphytic organisms (e.g., enhance assessment of potential nutritional resources diatoms) that grow attached to them (W. Leibfried and and their utility in nature. Montgomery unpublished). 28 29 Rainbow trout are visual and particulate remain somewhat passive at foraging sites and move (ingesting individual items) feeders, and thus usually from them to intercept drifting or other prey. An adult concentrate their feeding activity during daylight or rainbow trout will move among such locations and crepuscular periods (dawn, dusk) or at night when displace subordinate individuals in the process, usually downwelling light is sufficient to silhouette prey with little overt aggression, in a manner characteristic against a light background (Tippetts and Moyle 1978, of a local dominance hierarchy. Periods of foraging at Rogers et al. 1984, Angradi and Griffith 1990). Inherent these sites will also be interspersed with periods in periodicity in feeding is most evident where food is refuge sites in quiet waters beneath undercut banks or consistently available; trout feed most heavily at dawn rocky ledges. or dusk in hatchery self-feeding systems (Boujard and Leatherland 1992, Chen et al. 2002). The actual Significant differences in foraging behavior foraging periods of individuals or a particular stock are may also occur between wild and domesticated likely to vary, however, in response to prey availability, trout. Hybrids between wild and domesticated trout predator pressures, seasonal changes in behavior, and experience reduced survival in nature, apparently other ecological factors, and may well be modified because of increased risk-taking without a simultaneous by short-term learning (Riehle and Griffith 1993, improvement in predator avoidance behavior. Warburton 2003). For example, Tippetts and Moyle Domesticated rainbow trout are reared in the absence (1978) attributed unusually high epibenthic foraging in of predators and must compete for food thrown on the the McCloud River to turbid conditions that interfered water surface. Hatcheries may therefore select against with drift feeding in adult rainbow trout. predator avoidance, although this is not the only possible explanation for this altered behavior. Selection for rapid The ability to respond to changes in availability of growth under reduced predation pressure may shift the prey over relatively short periods is significant because optimal trade-off between energetic gain and mortality trout influence the drifting patterns and densities of risk in favor of “high gain-high risk” phenotypes. some prey. For example, nymphs avoid drifting Genes for predator avoidance may no longer contribute during the day in the presence of rainbow trout, and to fitness and may decrease in frequency or drift into are probably detecting trout through chemical means fixation. Furthermore, selection for large body size in (Douglas et al. 1994). Trout may experience extended the absence of predators will favor risk-prone and/or periods of low food availability, but food-deprived risk-indifferent foragers relative to more risk-averse fish often exhibit hyperphagia and considerable individuals (Johnsson 1992). compensatory growth following such stressful periods (Jobling and Koskela 1996). Breeding biology

Feeding territories of fry and juvenile trout may Rainbow and other western trout and salmon influence several aspects of trout ecology relevant to evolved primarily in the flowing water of small streams management (Gerking 1994). First, territories may be to large rivers, where they feed primarily on drifting interspecific and thus bring introduced rainbow trout invertebrates and small fishes. Pacific salmon, as well into conflict with native species. Conflict may lead to as some rainbow trout inhabiting coastal streams and physical damage, reduces foraging time, and likely rivers, evolved an anadromous habit as well. These increases stress hormone levels. Second, territory size fish spend variable numbers of juvenile years in the tends to increase with body size, declining food density river, migrate to sea where rich marine foods support and reduced current. Territoriality can lead (a) to growth to large size, and return to spawn in their natal displacement of subordinate individuals (Gilmour 2005) streams. Spawning habitat varies considerably among to habitats where they are more likely to be transported species and between sea-run (steelhead) and riverine downstream and suffer higher mortality or (b) to status rainbow trout. as “floaters,” non-territorial animals that experience lower food intake and other density-dependent During reproductive periods, a female digs a pressures. Such territories become potentially important depression in rocky (normally gravel or small cobble) regulators of population size. substrate with strong lateral flexions of her tail, all the while being attended and defended by a male. Digging Feeding behavior of adult rainbow trout differs also suspends and displaces fine sediments. Spawning from that of fry and juveniles. Unlike territorial involves simultaneous release of gametes by female juveniles, adults in streams tend to occupy home and male, after which the female digs upstream of the ranges with multiple foraging and refuge sites. Trout initial depression, displacing gravel downstream to bury 30 31 eggs laid there. This produces a single, buried “egg fertilize variable proportions of eggs laid, and thereby pocket.” The female then begins excavation of another competitively reduce the reproductive success of the spawning depression. One to several egg pockets may dominant male. be laid within a single nest area, termed a redd. Female fecundity varies with size (Figure 5). Eggs are aerated The continued artificial selection of rainbow by flow of water through the interstices of the gravel. trout in hatcheries has enabled this species to express Time to hatching is temperature dependent. Hatchlings elevated growth rates compared to those observed (sac-fry or alevins) possess large yolk sacs that support in natural populations or self-sustaining populations early growth. When most of the yolk is absorbed, the established in the past. If recently stocked fish grow fish move to the surface and to shallow, slow-moving to unusually large size and exhibit the expected water along stream edges and begin the free-living, proportional increase in fecundity (Figure 5), they exogenous-feeding stages of their lives. might competitively exclude the smaller and lower- fecundity previous residents. Biro and others (2004) Although much less studied than in some other suggest that greater body size potentially achieved by species (e.g., Atlantic salmon), rainbow trout are fish exhibiting elevated growth rates may not increase among a variety of salmonids whose small males fitness because of increased risk of predation associated exhibit “sneak” or “satellite” mating tactics when in with increased feeding required to achieve and maintain competition for spawning opportunities with large the large body. Domesticated rainbow trout are selected attending males (Montgomery 1983, Montgomery et for rapid growth and early maturity, characteristics al. 1987, Esteve 2005). Satellites may be parr or small often accompanied by a short life span, and they adults, both of which sacrifice additional growth by did not outgrow wild trout in a predator-free lake. channeling nutrients and energy into elaboration of Trade-offs between growth and mortality rates appear testes. These fish remain inconspicuous but near an to be associated with variations among populations actively digging female, do not court, and dart in to rather than within populations (Biro et al. 2004). Few emit milt (spermatozoa and accompanying fluids) domesticated rainbow trout survive more than one only when the female and larger attending male begin year in the wild after reaching sexual maturity (at to spawn. Both parr and small adult fish are fertile, approximately age 1 year) and therefore may normally

Rainbow Trout Fecundity

6000 eggs eggs/kg Linear (eggs) Linear (eggs/kg)

5000 y = -2.6561x + 5614.2 R2 = 0.6404 4000

3000 # eggs #

2000 y = 1.3818x + 1465.2 R2 = 0.4173 1000

0 200 400 600 800 1000 1200 1400 weight (g)

Figure 5. Rainbow trout fecundity related to weight. Lines represent linear regressions of total eggs per female (solid line) and eggs/kg per female (dashed line). Data combined from Blom and Dabrowski 1995, Gall and Gross 1978, and Su et al 1997. 30 31 spawn once or not at all. Most wild western trout will v Population-wide genetic variation may be first spawn at ages 2 to 4 years. Fecundity of western reduced due to (hatcheries) or rainbow trout is greatly influenced by environment as small population bottlenecks, where the well as heredity, and will ultimately influence the age few animals to survive and reproduce carry and size at first spawning (Behnke 1992). only a fraction of the total genetic variation in an original larger population. This tends Demography to reduce flexibility of responses to altered environmental conditions and to increase Genetic characteristics and concerns susceptibility to other threats. For example, recent studies of California golden trout Genetic analyses indicate that the salmonids arose indicate that lake populations experienced via autotetraploidy during matings between members of reductions in genetic diversity due to a series the same species (vs. allotetraploidy due to interspecific of bottlenecks and then suffered introgressive hybridization). As a result, whitefishes, graylings, hybridization with hatchery-reared and trout, and salmon possess four sets of chromosomes stocked rainbow trout (Gold and Gold 1976, (tetraploid condition) instead of the more common two Cordes et al. 2006). sets characteristic of diploid organisms. The formation of new taxa via tetraploidy has been studied extensively v Heterozygosity may be reduced (and thus in some groups (e.g., higher plants), and the additional homozygosity increased), so that for many genetic material may have supported the rapid evolution genes an individual possesses only one within the salmonids. allele at that gene. Higher heterozygosity has been correlated with increased disease Among populations of rainbow trout, chromosome resistance (Ferguson and Drahushchak 1990), number varies, indicating considerable dynamism in better condition (Danzmann et al. 1988), and chromosomal rearrangements (e.g., fusions, fissions) developmental stability (Leary et al. 1985) in through the evolutionary history of the species. The rainbow trout. diploid (2n) chromosome number of rainbow trout ranges from 2n = 58 to 2n = 64, but all share the same v Introgressive hybridization may lead to number of chromosome arms (104; Thorgaard 1983). disruption of highly evolved gene complexes Fish with the most common chromosome number, 2n in particular locales and thus reduce fitness = 58, appear to represent the ancestral condition for for animals occupying these locales. The populations exhibiting higher 2n numbers and presently fidelity of salmonids to spawning in natal range from Russia to coastal California (Phillips et al. streams has led to stocks highly adapted 2005). Deviation of a population from the widespread to specific sites (e.g., Marnell et al. 1987, 2n = 58 may suggest origins of stocked fish in areas ) and to genetic divergence among fish beyond the core native range of the trout. from different geographic locations (e.g., Docker and Heath 2003, Novak et al. no Ryman and Utter (1987) produced a valuable date). Several genetic studies demonstrate early compilation of information on salmonid introgressive hybridization between rainbow and the discipline’s relevance to . trout and other salmonids (especially various That volume identified key concerns that remain today, cutthroat stocks and subspecies - see below; including issues with genetic variation in wild and Young et al. 2001; Campbell et al. 2002). hatchery stocks, inbreeding effects, hybridization and introgression, and gene frequency shifts under the v Hatchery rearing may intentionally or influence of genetic drift and directional selection. unintentionally select for traits that enhance success in hatcheries but produce fish that The greatest management problems with perform poorly in the wild, in part because genetics of rainbow trout relate to limited genetic novel hatchery environments contribute to variation in small wild populations or hatchery stocks genetic divergence from a wild phenotype and associated inbreeding depression (loss of vigor, (Johnsson 1992). Miller et al. (2004) viability, fecundity, etc., related to loss of genetic demonstrated drastically reduced survival variation due to homozygosity). Specific concerns from hatching to age 1+ of hatchery rainbow relevant to management of rainbow trout popula- trout compared to naturalized (wild, but tions include: previously established from stocked fish) 32 33 fish (Miller et al. 2004). Sundstrom et al. As noted above, native trout populations, (2004), working with brown trout, found including cutthroats, often appear to have adaptive that hatchery-reared fish were more bold gene complexes that ‘fit’ the fish to local conditions. than wild fish and that bold fish tended to When disrupted by nonnative rainbow genes, this become socially dominant. In fact, effects of compromises the ability of native to thrive in hatchery rearing may be even more pervasive their local environments. than commonly recognized. Marchetti and Nevitt (2003) recorded differences in eight The decline of native cutthroat species (Varley brain measurements between hatchery reared and Gresswell 1988, Kershner et al. 1997, Ross 1997, and wild rainbow trout, with components of Henderson et al. 2000, Kruse et al. 2000, Hitt et al. hatchery fish brains consistently smaller than 2003), and in some cases the local disappearance of those of wild fish. The brain areas affected a distinctive cutthroat phenotype, is often attributed are known to influence such key activities to introgressive hybridization between introduced as predator avoidance, growth and gaining rainbow trout and native cutthroat species in Region access to appropriate mates. 2. Nonetheless, hybrids between native cutthroat and hatchery rainbows can produce large fish that meet Additional concerns with hybridization angler satisfaction (Ross 1997, Behnke 2002). Such use of hybrids may appeal to agencies because the Rainbow trout in waters of Region 2 provide fish exhibit accelerated growth rates to larger size than many recreational fishing opportunities, yet they also either parental species. For example, stocked create problems by hybridizing with native cutthroat rainbow x cutthroat hybrids in Ashley Lake through at subspecies, thereby threatening the genetic integrity of least August 2006; the lake produced the 30-pound, 4- cutthroat trout (Madeira et al. 2005, Ross 1997, Shepard ounce world record “” in 1982. There is also a et al. 1997). This contrasts with coastal cutthroat and psychological value in creating “new” organisms and native rainbow trout because they have evolved in therefore providing anglers with the opportunity to fish (Hitt et al. 2003) and have maintained for a new kind of prey (Ross 1997). reproductive isolation. Often associated with hybridization is partial or Both rainbow trout and cutthroat trout spawn in complete sterility. Stocking with sterile animals ensures the spring, react similarly to environmental cues that no reproduction and thus no hybridization or natural initiate spawning (Behnke 2002), and thereby create recruitment, but problems generated by higher densities an opportunity for gene flow between the two species and heavier competition may persist. (Kershner et al. 1997). In fact, Behnke (2002) suggests that when rainbow trout are introduced in waters Social patterns for spacing where native cutthroat populations exist, hybridization is the likely outcome. Cutthroat trout tend to occupy Like many fishes, rainbow trout exhibit a colder habitats than do other Oncorhynchus species, variety of social systems depending on age and size, but all other requirement for reproductive success population density, availability and type of habitat, food and threats to their existence are similar to rainbow availability, and experience. Fry in appropriate habitat trout (Behnke 2002). Hitt and others (2003) recorded will, as noted above, establish feeding territories. introgression hybridization between native westslope These territories may be defended against conspecifics cutthroat and planted rainbow trout, and concluded that as well as other species, and their size fluctuates with hybridization was spreading rapidly in an upstream food density. At low population densities, juveniles direction but might be reduced by erecting physical and adults may defend territories or, particularly in the barriers. Kruse et al. (2001) believe that reliance for case of locally dominant adults, move among multiple long-term conservation on Yellowstone cutthroat trout feeding and resting sites in a home range, simply populations isolated in headwater streams was unwise displacing subordinate fish from locations preferred due to small sizes of populations that made them more by the larger animal. At higher densities or in restricted susceptible to genetic drift (change in allele frequencies habitat, juveniles and small adults, including recently that occurs entirely from chance) or unpredictable stocked hatchery fish, often form aggregations in the environmental conditions. water column near shore or in other areas of slowly flowing water.

32 33 Pattern of dispersal of young and adults and are known to eat fishes, including some species of water (Natrix) and garter (Thamnophis) snakes, Dispersal of young begins, as noted elsewhere, and predatory invertebrates to lists of likely predators by recently emerged fry moving to quiet near-shore (Table 6). Similarly, estimates of the intensity of threats locations where they establish feeding territories. from predators should be based on the densities and Individuals incapable of winning and holding a territory predatory tactics of predators relative to the habitat and or other site for persistent occupation will normally be behavior of different trout life history stages. Fry in displaced to suboptimal habitat. Fry and juveniles in shallow nearshore waters, for example, are more likely such circumstances may be flushed from their initial to be attacked by snakes, wading birds, and giant water site of occupancy by strong currents, particularly at bugs or crayfish than later life history stages, while adult night when their visual orientation and ability to hold trout in lakes or higher order streams with open canopy station is compromised. In a somewhat similar fashion, will be more susceptible to raptors than wading birds. juveniles and adults move preferentially downstream during the winter in order to find deeper and more Competitors persistent habitats for overwintering. Spring may see spread of fish from downstream to upstream habitation Competition is frequently cited as an important and, for mature fish, spawning sites. During spring, factor controlling size of animal and plant populations, summer and into fall, many trout remain restricted in yet its existence is more often inferred than their movements, moving tens to a few hundred meters. demonstrated through controlled experiment (Connell Others may move several kilometers. 1980, Weber and Fausch 2003). The lack of resource overlap between two species, for example, may reflect Limiting factors either (a) no competition for that resource or (b) the result of intense competition and competitive exclusion A wide array of limiting factors has been noted by one species of another. in preceding sections. Habitat for any of the major life history stages is crucial. The amount of available Nonetheless, patterns consistent with competitive spawning habitat will limit the number of eggs that are interactions among animals (e.g., local ; likely to complete development. Insufficient fry habitat displacement in space, time, or food use; fragmentation will result in high mortality of this stage and reduced of once continuous populations; altered patterns of recruitment of juveniles and, subsequently, adults. Food behavior; different size distributions or condition in supply may also be restricted due to low reproductive and out of areas where competition occurs) appear success of food organisms or suppression of food commonly throughout the expanded range of rainbow availability through predation by rainbow trout or other trout. Depending on the circumstances, competition fishes. Negative interactions with other species may may be expressed through direct interaction or include competition with conspecifics or other species, conflict between individuals over a resource (“contest” cannibalism by larger trout, predation by both aquatic competition) or through “exploitation” competition and terrestrial organisms, and and disease, all where both use the same resource but differ in their touched on in more detail below. volume or efficiency of use. Although competitive interactions may be asymmetric (affecting one of the Predators competing animals or life history stages more than the other), both competitors suffer negative effects such as Given the diversity of habitats occupied by reduced access to a resource or physical damage from rainbow trout during their various life stages, they are direct conflict. potentially susceptible to virtually any predator that feeds underwater or on fish occupying shallow, near- Furthermore, the nature and severity of competitive shore, or near-surface environments (Table 6; Tabor effects may differ with taxonomic relationship of and Wurtsbaugh 1991, Lovvorn et al. 1999, Zimmerman the interacting animals; intense competition is more 1999, Kerr and Lasenby 2000 and references therein, likely between closely- than distantly-related species Laake et al. 2002, Gard 2005). Thus, managers should (Ross 1986). Species that may compete with rainbow make independent assessments of likely predators based trout are taxonomically diverse (Table 7), but most on the behavior of predators in the area of concern detailed research has focused on competition between rather than on existing reports of animals known to take conspecifics (other rainbow trout) or between rainbow rainbow trout. This approach would, for example, add trout and other salmonids. This reflects the expectation both snakes that forage in or adjacent to stream systems that broad similarities in habitat use, feeding patterns, 34 35 Table 6. Known or likely predators of rainbow trout, including steelhead. (Brown and Diamond 1984, Tabor and Wurtsbaugh 1991, Parkhurst et al. 1992, Brown and Brasher 1995, Derby and Lovvorn 1997, Lovvorn et al. 1999, Zimmerman 1999, Jepsen et al. 2000, Kerr and Lasenby 2000 and references therein, Laake et al. 2002, Jonas et al. 2005, Anonymous 2006, personal observation) Mammals Predatory fishes Bear Brown trout Burbot Mink Chain pickerel Otter Channel catfish Raccoon (Anguilla – freshwater stage) Lake trout Birds Largemouth bass American crow Northern pike Bald eagle Belted kingfisher Pikeperch Rainbow trout Common tern Common grackle Double breasted cormorant Sculpin Great blue heron Smallmouth bass Green-backed heron Spotted bass Mallard Striped bass Merganser Tiger muskie Osprey Utah chub Pelican Walleye Western grebe Yellow perch

Snakes Invertebrates Garter snakes (Thamnophis) Water snakes (Natrix) Crayfish Freshwater amphipod - Giant water bugs - Hemipera Phantom crane flies Stoneflies -

and life history among salmonids are likely to engender rainbow trout conferred fewer benefits than at lower competitive interactions in areas of sympatry. population levels (Li and Brocksen 1977), and the competitive advantage of large body size declines with Intraspecific competitive interactions affect a increasing group size (Pettersson et al. 1996). variety of life history and behavioral characteristics. Increasing competition for scarce food resulted in Time of stocking may influence subsequent levels higher mortality, higher willingness to emigrate, higher of competition between resident and released fish. variance in body mass, lower growth, lower population Hatchery-raised steelhead smolts went to sea soon after density, and lower in juvenile steelhead. The planting, avoiding common effects of competition and size of their contiguous territories decreased with predation (Hayes et al. 2004). increasing density and increased with increasing size (Imre et al. 2004), and density declined with increasing Interspecific interactions between rainbow trout mass (Keeley 2003). At higher densities, dominance in and other salmonids suffer added complexity due to 34 35 Table 7. Recent reports of known, likely and unlikely competitors of rainbow trout. Species Common name Reference Known or likely: Salmonidae Oncorhynchus clarki henshawi Peacock and Kirchoff 2004 O. kisutch Bonar et al. 2005 O. masou masou salmon Morita et al. 2004 O. mykiss rainbow trout, steelhead Hayes et al. 2004 O. nerka kokanee Schneidervin and Hubert 1987 Salmo salar Atlantic salmon McKenna and Johnson 2005 Salmo trutta brown trout Scott and Irvine 2000, Hayes 1987 Salvelinus fontinalis brook trout (brook charr) Lohr and West 1992 white-spotted charr Morita et al. 2004 grayling Honsig-Erlenburg 2001 Gila atraria Utah chub Schneidervin and Hubert 1987 Lepidomeda vittata Little Colorado spinedace Robinson et al. 2003 Ptychocheilus grandis Sacramento pikeminnow Reese and Harvey 2002 Rhinichthys osculus speckled dace Robinson et al. 2003 balteatus redside shiner Reeves et al. 1987 Catostomus catostomus longnose sucker Trojnar and Behnke 1974 C. commersoni white sucker Schneidervin and Hubert 1987 C. discobolus bluehead sucker Robinson et al. 2003 Perca flavescens yellow perch Fraser 1978 Gastrerosteidae Gasterosteus aculeatus threespine stickleback Vamosi 2003 brevipinnis koaro Kusabs and Swales 1991 Other [Not specified] Jackson et al. 2004 Ambystoma tigrinum tiger salamander Olenick and Gee 1981 Invertebrates Euastacus spp. Australian spiny crayfish Jackson et al. 2004 Unlikely: Anguillidae Anguilla bengalensis African mottled Butler and Marshall 1996 Cyprinidae funduloides rosyside dace Rincon and Grossman 1998 Salmonidae O. tshawytscha chinook salmon McMichael and Pearsons 1998 Salmo trutta brown trout Lucas 1993 Salvelinus fontinalis brook trout Strange and Habera 1998

36 37 Table 7 (concluded). Species Common name Reference Ambloplites ariommus Fenner et al. 2005 Lepomis macrochirus bluegill sunfish Fenner et al. 2005 Micropterus dolomieu smallmouth bass Fenner et al. 2005 M. salmoides largemouth bass Shrader and Moody 1997 Other vertebrates Aonyx capensis Cape clawless otters Butler and Marshall 1996 The list is not exhaustive, but includes reports from locales in North America, Europe, Japan, Australia and New Zealand to emphasize the diversity of real or suspected competitors. Because competitive interactions affect both competing taxa, this also indicates where rainbow trout may impose competitive pressures on other species.

their possession of both highly similar and yet species- the western United States. However, these interactions specific patterns of behavior and communication. For are not always negative. Nilsson and Northcote (1981) example, in staged contests between juvenile steelhead describe how apparent habitat displacement of cutthroat and coho salmon, steelhead tended to display more than trout by rainbow trout resulted in more piscivory and coho, larger fish chased more while small fish displayed a higher growth rate by cutthroat trout. Similarly, more, and the larger fish won consistently independent rainbow trout are not always the winners in competitive of species (Young 2003). When rainbow trout were interactions. Schneidervin and Hubert (1987) proposed pitted against juvenile Atlantic salmon, resident fish that competition for food among rainbow trout, always outperformed challengers, regardless of species introduced kokanee, Utah chub (Gila atraria) and white (Volpe et al. 2001). This was consistent with McKenna sucker (Catostomus commersoni) in Flaming Gorge and Johnson’s (2005) assessment that rainbow trout and Reservoir contributed to limited stocking success of juvenile Atlantic salmon occupied similar ecological the trout. niches in Lake Ontario drainages, but the competitive effects of the trout apparently declined with increasing The nature of competition is such that studies tend temperature (Coghlan 2005). Rainbow trout were to focus on the interactions of species and often overlook also competitively superior to white-spotted charr subtle influence of environment on competition or the (Salvelinus leucomaenis), but not the sympatric masou secondary effects that competitive stress may exert on salmon in Japan (Hasegawa 2004, Morita et al. 2004). the general health of interacting species. For example, competitive interactions of rainbow trout with various Ecological and behavioral similarities across fishes may be weakened in warm waters. On the salmonid taxa extend to reproductive activity as basis of little dietary overlap between trout and three well as the more commonly addressed feeding and native warmwater fishes (smallmouth bass, shadow habitat. Interference-competition involving redd bass, bluegill sunfish), Fenner et al. (2005) doubted superimposition of brown and rainbow trout (Hayes that competition for food occurred. Steelhead held 1987) limited spawning success of both species (egg with Sacramento pikeminnow exhibited much poorer deposition to fry emergence: 2.1 percent for rainbow growth at 20 to 23 ºC, when pikeminnow initiated more trout, 0.2 percent for brown trout). Late spawning interactions with trout, than at cooler temperatures (15 rainbows experienced the highest spawning success. to 18 ºC) (Reese and Harvey 2002). Similarly, steelhead Spring-spawning rainbow trout superimposed 13 dominated steelhead/redside shiner interactions at low percent and 3 percent of native, fall-spawning Dolly (12 to 15 ºC), but not high (19 to 22 ºC), temperatures Varden (Salvelinus malma) and white-spotted charr in a (Reeves et al. 1987), but even these relationships can small stream in , Japan. be complex. In aquarium and stream tank experiments, small, subordinate steelhead escaped damage from As inferred by the list of real or potential dominant steelhead by joining groups of shiners (Tinus competitors of rainbow trout (Table 7), the nature of and Reeves 2001). interspecific competitive interactions faced by rainbow trout is likely to include both contest and exploitative Furthermore, competitive interactions and the forms of competition. Many of these interactions lead to status resulting from them may generate physiological concerns over the fate of native fishes, including several effects in rainbow trout that are difficult to detect cyprinoids and various subspecies of cutthroat trout in but that may reduce their performance or viability in 36 37 nature. For example, Li and Brocksen (1977) recorded if those parasites have no effect on tissue quality and increased variance in routine metabolism, growth rate, pose no threat to humans, may generate problems consumption rate, and growth efficiency with increased ranging from declines in the number of licenses sold to density, all likely due to intraspecific competition. negative media reports. Subordinate rainbow trout had higher rates of sodium uptake across the than dominant fish (Sloman et al. It behooves fisheries personnel to develop at least 2004), apparently due to changes in gill permeability a fundamental understanding of the major categories that resulted in higher throughput of water and of fish parasites, including the means to identify them, increased sodium efflux. Such changes may increase their basic life cycles, the maladies they may cause, and susceptibility to ion regulatory challenges and increase best practices for preserving samples for subsequent metabolic cost of ion regulation. Subordinate animals accurate identification by trained professionals. Even may avoid competition with dominant fish by shifting armed with such knowledge, a manager’s options for feeding and activity cycles, behaviors involving the control or elimination of many parasites are highly pineal and its hormone melatonin. Social stress affects constrained. Effective treatments are often unknown, circulating melatonin (Larson et al. 2004). and existing chemical safety regulations limit the number of compounds allowed for treatments of fishes Parasites and disease intended for human consumption or of water that may be released into the environment. Additional information on Rainbow trout may harbor a wide array of regulations about, and compounds potentially available parasites, but few appear to exert strong impacts on fish for, treatment of parasites and other fish diseases may in Region 2. Buchmann et al. (1995) found published be found in Nickum et al. (2004) and on the website reports of 169 taxa of parasites from rainbow trout for the U.S.Fish and Wildlife Service (2005) Aquatic worldwide, including representatives of seven major Animal Drug Approval Partnership Program (http: animal groups: Monogenea - monogenetic trematodes //www.fws.gov/fisheries/aadap/ACCESS/states.html). (single host in the life cycle), Digenea - digenetic trematodes (more than one host in the life cycle), As noted previously, the greatest parasitic threat Cestoda - tapeworms, Nematoda - roundworms, to rainbow trout in Region 2 at present is whirling - thorny-headed worms, Crustacea - disease. Caused by a metazoan, , and their relatives, and Hirudinea - leeches. the disease affects stream-dwelling salmonids in the These same major categories have also been recorded northeastern and western United States. Infected fish from Region 2, as have representatives of additional may have a darkened tail, twisted spine, or deformed groups including bacteria, fungi, ciliates, flagellates, head (shortened, twisted jaws). Young fish may also myxozoans (cause of whirling disease, the greatest swim erratically (whirl). While other diseases and concern to fish managers in the western United States even genetic conditions can cause these signs as well, and elsewhere), and microsporidians (Table 8). managers should request immediate reports of any fish exhibiting such symptoms. Clearly, the diversity of potential parasites is high. Nonetheless, the simple presence of a parasite in Region The life cycle of the parasite requires two 2 may not be a cause for alarm, but the potential for hosts (Figure 6): a fish and an worm. Larval transmission to rainbow trout increases with occurrence Myxobolus cerebralis colonize the head and spinal of a parasite in cool waters or in other species of cartilage of fingerling trout, reproduce rapidly, damage salmonid fishes and their relatives (e.g., golden, brown cartilage, and place pressure on the nervous system. and cutthroat trout, ). On the other Damage to the skeletal and nervous systems cause the hand, infection by parasites such as the causative fish to swim erratically, often uncontrollably in circles, agent of whirling disease, Myxobolus cerebralis, may making them particularly susceptible to predators and have massive economic and practical impacts, with interfering with their ability to feed. When an infected destruction of large numbers of fish and/or closure of fish dies, large numbers of M. cerebralis spores (each a hatchery until it is subsequently certified as parasite- about the size of a red blood cell) are released into the free. Similarly, rates of transmission to and among water and settle in sediments. Spores are subsequently rainbow trout in the wild are likely to be much lower eaten by , a segmented (annelid) worm than among hatchery fish held in high-density rearing that lives in fine sediments. Spores then transform into facilities, although whirling disease in particular may an active, infective larval stage termed a triactinomyxon wreak havoc on wild stocks of trout (see below). Finally, that is released into the water. Triactinomyxon larvae visually obvious parasites in fish taken by anglers, even float in the water until they contact a fish host, renewing 38 39 Table 8. Examples of major groups and genera of parasites recorded from rainbow trout or other salmonids. (Becker and Brunson 1967, Buttner and Hamilton 1976, Ching 1984, Weekes and Penlington 1986, Woo and Wehnert 1986, Dick et al. 1987, Szalai and Dick 1988, Bates and Kennedy 1990, Dies 1990, Buchmann et al. 1995, Mitchum 1995, Buchmann and Bresciani 1997, Varley and Schullery 1998, Pottinger and Day 1999, McKinney et al. 2001, Choudhury et al. 2004, Gieseker et al. 2006, FAO Fisheries and Aquaculture Department (no date).) Bacteria Digenean trematodes Aeromonas (golden trout) Apophallus (brook trout) Clinostomum Fungi Crepidostomum (brook trout) Ichthyophonus Diplostomum Saprolegnia (brown trout) Tylodelphys Ciliates Cestodes Amblphrya Bothriocephalus Apiosoma Corallobothrium Capriniana (cutthroat trout) Chilodonella Ligula Epistylis Proteocephalus (cutthroat trout) Ichthyophthirius Trichodina Acanthocephala Trichodinella Acanthocephalus Flagellates Pomphorhynchus Costia Nematodes Hexamita Capillaria (cutthroat trout) Ichthyohodo Truttaedacnitis Capillaria (cutthroat trout) Microsporidia Contracaecum Cystidicola Nucleospora Eustrongylides Parasitic Crustacea Henneguya (mountain whitefish) Argulus (unidentified salmonid) Myxobolus Ergasilus Tetracapsula Lernaea Salmincola (cutthroat trout) Monogenean trematodes Dactylogyrus Leeches Eubothrium unidentified genus (cutthroat trout) Gyrodactylus (cutthroat trout) Piscicola Proteocephalus Tetraonchus (mountain whitefish) Triaenophorus as presented in original source. Photographs of a wide variety of the Wyoming parasites on host fishes are available at: http://gf.state.wy.us/downloads/ppt/parasitesofwyomingfishes.ppt and http://gf.state.wy.us/downloads/pdf/parasitesofwyomingfishes.pdf.

38 39 Figure 6. Life cycle of the whirling disease parasite. Matbouli et al. 1992 . the cycle. At present, once established in a stream, the 1998). Similar declines have been reflected in poor parasite cannot be eradicated, nor can its worm host, recruitment in the Middle Park sections of the Colorado without potentially damaging the . Whirling River, which previously supported high densities of disease has no known human health effects. age-0 rainbow trout (Nehring and Thompson 2001 cited in Sipher and Bergerson 2005). The parasite can Until the 1990’s, Myxobolus cerebralis was also be spread in its spore form by birds and humans primarily a problem in hatchery settings, but that (particularly boaters and anglers) and their equipment. changed rapidly (Gilbert and Granath 2003). In drainage basins where M. cerebralis has been detected, Myxobolus cerebralis appears capable to infect all wild rainbow trout populations have declined in both salmonid fishes, but susceptibility to infection differs Montana (Vincent 1996, Baldwin et al. 1998) and among species (Table 9). Gilbert and Granath (2003) Colorado (Nehring and Walker 1996). For example, noted that although rainbow trout are most susceptible from 1978 to 1991, Montana’s to disease, the parasite is able to infect numerous supported a stable wild trout fishery (Vincent 1996). species of salmonid fishes, including sockeye salmon, Rainbow trout populations plummeted, however, from golden trout, cutthroat trout, brook trout, bull trout 3,300 fish per mile estimated in 1991 to 300 per mile (Salvelinus confluentus), steelhead, chinook salmon, in 1995 along a 56-mile section of the river (D. Vincent Atlantic salmon, and brown trout. All subspecies of personal communication cited in Rognlie and Knapp cutthroat trout and the mountain whitefish are also quite 40 41 Table 9. Susceptibility to whirling disease among species of salmonids found in Region 2. Species Common Name Susceptibility Code Oncorhynchus mykiss Rainbow trout 3 Oncorhynchus mykiss Steelhead 3 Oncorhynchus clarki bouveri Yellowstone cutthroat 2 Oncorhynchus clarki lewisi West slope cutthroat 2 Oncorhynchus clarki pleuriticus cutthroat 2 Oncorhynchus clarki virginalis Rio Grande cutthroat 2 Oncorhynchus clarki stomisa Greenback cutthroat 2 Salvelinus fontinalis Brook Trout 2 Salvelinus confluentus Bull trout 1 Salvelinus namaycush Lake trout 0 S Salmo trutta Brown trout 1 Prosopium williamsoni Mountain whitefish 2 S Based on laboratory or natural exposure to Myxobolus cerebralis at vulnerable life stages. Suceptibility: 0 = resistant, no spores develop; 1 = partial resistance, disease rare and develops only when exposed to very high parasite doses; 2 = susceptible, clinical disease common at high parasite doses, but greater resistance to disease at low doses; 3 = highly susceptible, clinical disease common; S = susceptibility is unclear (conflicting reports, insufficient data, lack ofM. cerebralis confirmation). Modified from: Whirling Disease Initiative, Montana Water Center, Montana State University, Bozeman, Montana 59717; http://whirlingdisease.montana.edu/about/transmission.htm.

susceptible. In recent years, however, considerable Colorado, it occurs in all coldwater drainages except interest has focused on rainbow trout strains, particularly the Animas and North Republican rivers. In 1998, 11 the Hofer strain from , that exhibit reduced of Colorado’s 16 hatcheries were contaminated by the susceptibility to the parasite. Susceptibility to infection parasite, but due to eradication efforts by the CDOW, also depends on the age of the fish Table( 10). Young by December 2004 just six were still considered individuals whose cartilaginous skeletons have not been positive for the parasite. The state imposes fish health fully replaced by bone are particularly susceptible. inspections on public and private hatcheries and fish culture facilities, requires a fish health disease Whirling disease has not been detected in certification on imported fish, has an extensive whirling Kansas, Nebraska, or South Dakota (Whirling Disease disease research program, and instituted a policy in Initiative website, http://whirlingdisease.montana.edu/ 2000 that calls for the cessation of stocking of any default.asp).There is no monitoring for the disease in WD-positive trout into any waters with self-sustaining Kansas because trout fishing is a put-and-take fishery salmonid fish populations. using certified whirling-disease-free private hatchery fish. Nebraska conducts a monitoring program for state Whirling disease was first detected in Wyoming and private hatchery fish that are exported. In South in 1988 (Wyoming Game and Fish Department 2008b), Dakota, importation and transportation of potential and as recently as April 2008, whirling disease was carriers of the disease are regulated, and all hatcheries discovered in one of the state hatcheries and in fish are screened annually for the disease. recently transferred from that hatchery to two other rearing stations (Wyoming Game and Fish Department Whirling disease has been known from Colorado press release, 1 April 2008). Managers have moved since 1987 (Colorado Division of Wildlife 2008). In rapidly to identify possible infections elsewhere in the

Table 10. Relationship between life history stage of a fish and the likelihood that stage may transmit whirling disease. Life history stage Source of parasite & parasite stage Likelihood of detection Eggs* No Not applicable Fry, alevins Yes – immature parasite stages Low to high Juveniles, adults Yes – spores Moderate to high *assumes disinfection and no transfer of water or material that might carry the parasite. Modified from: Whirling Disease Initiative, Montana Water Center, Montana State University, Bozeman, Montana 59717; http://whirlingdisease.montana.edu/about/transmission.htm.

40 41 hatchery system, and have moved plans for renovation to both hatcheries and natural waters. Thus, although of the affected hatchery to the top of the priority list. attention in what follows focuses on human and other State regulations forbid release of live fish or fish eggs natural threats, several types of threats derive from the without the consent and supervision of the WYGFD or various trout stocks themselves. transport of live fish or live fish eggs from the water of capture. Rainbow trout fishery declines, and in some cases collapses, have been attributed to increased Symbiosis human activity that has directly altered the original coldwater habitats of this group of fishes. Some The term symbiosis describes relatively stable examples of human activities directly affecting fisheries relationships between two (or more) species. The are hydropower development, forest management, concept in its simplest form encompasses mutualism, livestock grazing, road development, logging, and where both organisms benefit from the interaction; mining (Everest et al. 1989). commensalism, where one benefits and the other is not harmed; and parasitism, where one benefits and the other Work directed at maintaining healthy trout is harmed. Excluding parasites (addressed elsewhere in fisheries result in a variety of secondary benefits, this assessment) and gastrointestinal microbes recorded including improved water quality, mitigation of droughts from rainbow trout (e.g., see Cahill 1990, Huber et al. and floods, increased groundwater replenishment, 2004), we are aware of a single symbiosis (an apparent improved wildlife habitat, improved recreational commensalism) involving rainbow trout. Small opportunities, increased cycling and movement of steelhead will take refuge in groups of redside shiner nutrients, maintenance of biodiversity, and increased (Richardsonius balteatus) to escape competitive attacks economic values (from recreation and tourism, real from larger steelhead (Tinus and Reeves 2001). estate, and water availability; www.tu.org).

MANAGEMENT AND Rainbow trout and other fishes require complex CONSERVATION aquatic habitats and healthy riparian zones to establish and maintain reproducing populations. Both aquatic and riparian habitats have been declining because Conservation Status of Rainbow Trout of increased human activity over the last several in the Rocky Mountain Region decades. For example, excessive sedimentation due to agricultural, mining, road-building, logging, and other As noted elsewhere, rainbow trout are not activities reduces primary and production native to any of the Region 2 states. The International (a major portion of trout diets), destroys submerged Commission on Zoolotical Nomenclature (1999) does aquatic vegetation (important for cover), and fills not list rainbow trout. NatureServe (2006) ranks the crevices and rocky interstices (refuges for small fish species as secure (G5). Two subspecies (California and eggs). While the following list of threats to rainbow golden trout and Inland redband trout and redband trout is not comprehensive, it does include topics of steelhead (Oncorhynchus mykiss gairdneri)) have particular relevance to Region 2. been introduced into Colorado, with the former also introduced to Wyoming; NatureServe (2006) ranks for Anthropogenic disturbance the golden and redband subspecies are G5T1 and G5T4, respectively, in their native ranges. Agriculture

Potential Threats to Trout Populations Many activities associated with rangeland management and farming activities adjacent to flowing Resource managers face a difficult balancing act or standing waters will affect fish habitats directly or in the western United States, where rare native species indirectly. Fortunately, these effects can be reversed concerns and now-wild rainbow trout management to varying degrees given careful thought and planned may conflict with constituent-driven trout stocking habitat management (Bowers et al. 1979). programs. Wild rainbow trout may displace native cutthroat stocks and at the same time are displaced Irrigation: In 2000, agricultural irrigation or otherwise compromised by hatchery trout accounted for approximately 90 percent of Colorado’s introductions. In turn, hatchery rainbow trout have total annual water consumption; values for other introduced whirling and other diseases and parasites Region 2 states were Kansas – 56 percent, Nebraska 42 43 – 71 percent, South Dakota – 71 percent, and year trout constitute major fractions of fish observed Woming – 87 percent (USGS, http://water.usgs.gov/ or dying in canals. Irrigation withdrawals can also watuse). Particularly relevant to fisheries managers disrupt spawning, increase , increase water is the fact that control of and priority for use of temperatures above tolerable levels, and increase local available water varies across states and usually rests population densities and density-dependent interactions in the hands of entities other than state or federal (e.g., competition, predation; see Der Hovanisian resource management agencies (also see section on 1995). In portions of the Snake River and its major Outdated Water Rights Systems below). Examples tributaries, reservoirs and irrigation diversions have from Region 2 states include Colorado - Division of resulted in reduced streamflows, degraded water- Water Resources, Water Conservation Board, Ground quality conditions, loss of habitat, and proliferation of Water Commission, Department of Public Health and non-native, warmwater species of fish (Maret 1995 in Environment (Water Quality Control Division); Kansas Clark et al. 1998). - Department of Water Resources, Department of Health and Environment (Bureau of Water); Nebraska Cattle grazing: Grazing, particularly on public - Department of Natural Resources, Department of lands controlled by the USFS and other federal and Environmental Quality (Water Quality Division); South state agencies, has become a tremendously contentious Dakota - Department of Environment and Natural issue in the western United States. As an internet search Resources; Wyoming - State Engineer, Department of for sites dealing with public lands grazing will verify, Environmental Quality. Furthermore, legislation may many believe that damage caused by cattle grazing to influence water management practices directly. For aquatic and terrestrial systems on these lands represents example, legislation in Colorado makes adherence to a failure of management agencies to protect valuable various “best management practices” for irrigation natural resources while artificially perpetuating an voluntary (e.g., Waskom 1994), and while application industry romanticized for more than a century in of better irrigation management and technology literature and film. increases, motivation to make such improvements tends to be constrained by practical (e.g., time and effort Insofar as fishes and fisheries are concerned, constraints, perceived sufficiency of available water) or uncontrolled grazing along streams, ponds, and economic concerns (Bauder et al. 1999). wetlands leads to excessive disturbance of naturally occurring banks as well as damage to structures placed Irrigation and irrigation practices have long by various stream enhancement projects (Binns 2004; affected rainbow trout and other fishes in a variety www.ngpc.state.ne.us), and will cause root bound of ways (Clothier 1953a reviewed in Der Hovanisian trees to collapse. Trees provide fish with cover and 1995). Particularly problematic are irrigation canals food, as well as keep the water cool. As banks erode, with high flow rates compared to those of the source there is an increased level of silt in the water that can stream (high flow ratios). These conditions may be suffocate eggs as well as abrade fish gills (Giuliano influenced by placement of intakes adjacent to wing 2006). Changes to vegetation adjacent to watercourses, dams, on curves of rivers, or near other types of from plowing pastures, planting and harvesting farm diversions that increase current velocity, inject fish into crops, or replacing a forest with a pasture, directly canals, or inhibit return to the source river (with greatest affect available resting and hiding cover and increase influence on young or small fish; Der Hovanisian 1995). water temperatures. Grazing activities have led to major Fish moving downstream and young-of-the-year fish declines in both native and nonnative trout species are often drawn into headgates while fish moving to throughout Region 2. upstream spawning or other sites have difficulty passing irrigation diversions and are often swept into irrigation The Federal grazing fee, which applies to Federal canals (Anonymous 2003). Extensive cover, including lands in 16 western states on public lands managed by areas where pools form, also increases losses as fish the Bureau of Land Management (BLM) and the USFS, take refuge as water levels drop rather than return to the is adjusted annually and is calculated by using a formula source stream (Der Hovanisian 1995). originally set by Congress in the Public Rangelands Improvement Act of 1978. These 16 states include Secondary and age- or size-specific effects exert all Region 2 states as well as Arizona, California, considerable influence on irrigation-related loss. High Idaho, Montana, , , North Dakota, population density and proximity to spawning areas Oklahoma, Oregon, Utah, and . Under this increase the likelihood that rainbow trout and other formula, as modified and extended by a presidential fishes will be entrained into the canals; young-of-the- Executive Order issued in 1986, the grazing fee cannot 42 43 fall below $1.35 per animal unit month (AUM); also, Roads, road construction, stream any fee increase or decrease cannot exceed 25 percent channelization, population fragmentation of the previous year’s level. An AUM is the amount of forage needed to sustain one cow and her calf, one The use of roads and construction of new roads horse, or five sheep or goats for one month. The grazing or other development projects adjacent to streams fee for 2008 is $1.35 per AUM, the same level as it was have serious implications to fisheries due to habitat in 2007. The figure is adjusted each year according to degradation. Roads and developments constructed in three factors: current private grazing land lease rates, valleys take advantage of relatively flat topography beef cattle prices, and the cost of livestock production. and gentle valley gradients; thus, they also generally In effect, the fee responds to market conditions, with lie near or along streams and rivers. Problems arise livestock operators paying more when conditions are when the width of a valley becomes restricted as this better and less when conditions decline. Without the frequently leads to roads that occupy, realign, encroach requirement that the grazing fee cannot fall below $1.35 on, and cross stream channels (Ruediger and Ruediger per AUM, the 2008 fee would have dropped below one no date). Affected stream segments are generally dollar per AUM because of declining beef cattle prices shorter than before alteration, with higher gradients, and increased production costs from the previous year. swifter currents, larger grain substrata over the long term (construction and subsequent bank or hillside Logging for timber and for water erosion will increase sediment load), few slow-moving backwaters, and reduced riparian communities. Banks Logging activities reduce intragravel dissolved may be stabilized by riprap, eliminating undercut oxygen concentrations because stream temperatures bank refuges, and road crossings may impede or halt increase after the riparian canopy is removed; logging upstream movements of fishes, leading to population also increases fine sediment concentrations (Bjornn fragmentation (Dunham et al. 1997). In general, habitat and Reiser 1991). Some Colorado state officials have complexity is much reduced, and both spawning and advocated logging state and national forests to increase rearing habitat for rainbow trout and other salmonids the amount of water available for use in streams are largely eliminated in the affected sections. Road rather than for feeding dense trees in high elevations. construction also leads to release of toxic chemicals Research has shown that between 25 and 40 percent of associated with cement and phenolic compounds from the watershed forest would need to be cut to produce road surfacing compounds (Crisp 1993). the desired increase in water yield. The increase would come in wet years where there is more than enough Managers should expect surprises in the nature water, and reservoirs would need to be constructed to of developments that can influence aquatic ecosystems catch the water for future need. Logging for water would and fisheries. For example, whitewater parks are ultimately be catastrophic for local stream fisheries due becoming popular in Region 2. One website (http:// to increases in sediment and muddy waters, loss of www.ripboard.com/community/whitewaterpark.shtml) woody debris that provides important trout habitat, and lists 11 such parks in Colorado with another four increases in water temperature due to decrease in shade planned or under construction in Colorado; one (www.tu.org). whitewater park is in Wyoming. Basic features of whitewater park construction suggest considerable Mining local impact on trout fisheries and water quality. These parks use boulders set in cement to mimic natural Hard rock mine waste, which is believed to be the river features such as waves and holes with associated single largest polluter in the United States, contaminates plunge pools, fast flowing water in mid-channel areas, over 40 percent of the headwaters of western and lateral and mid-channel eddies (McGrath 2003). watersheds. There are nearly 500,000 abandoned mines Individual instream structures may create different across the west. In Colorado alone, there are 20,299 hydraulic features during low, medium, or high flow abandoned mine sites and approximately 1,300 miles conditions. Stream bank stabilization, re-grading and of adversely affected waters (www.tu.org). Elevated terracing, footpath construction, and terraced riparian concentrations of arsenic, cadmium, copper, lead, and revegetation are common in park design. zinc near mines or in affected waters may be fatal to fishes as they cause hypertrophy, degeneration and Aquatic hitchhikers/nuisance organisms necrosis of epithelial cells that support normal gill function (Farag et al. 2003). The ecological balance of waters in western states has been compromised by introductions and/or 44 45 accidental arrivals of a number of organisms, some Energy development of which have been specifically identified as “aquatic nuisance species” (ANS). Collectively, the five The BLM and the USFS are proposing Region 2 states have identified at least 29 species as unprecedented levels of gas, oil, and coal bed methane such, including one alga (“didymo” - Didymosphenia exploration and extraction on public lands, with possible geminata), nine flowering plants [saltcedar, Tamarix severe impacts on crucial fish and wildlife habitats spp., is included due to its influence on riparian throughout Montana, Wyoming, Colorado, Utah, and communities], a freshwater jellyfish (Craspedacusta New Mexico. The White House has placed an emphasis sowerbyi), the rusty crayfish (Orconectes rusticus), six on domestic energy production as a matter of national molluscs, 10 fishes, and the American bullfrog (Rana security. and other conservation catesbaiana). Although some species (e.g., American organizations believe that short-term energy production bullfrog) occur in all five states, no species is recognized should not result in diminished long-term productive as present (and thus ANS) on more than three state lists, capabilities of lands and water that sustain us in a variety reflecting a desire by states to identify those organisms of ways. Protection of critical fish habitat and migratory most likely to cause or have the potential to cause corridors should remain a priority as responsible energy damage to existing aquatic communities. Some state production takes place (www.tu.org). lists also include species not yet recorded from that state, particularly if they have been reported from Chemical pollution adjacent or nearby states or are known to be rapidly expanding their range. For example, hydrilla (Hydrilla Effluent from a wide array of domestic, verticillata) was listed as not yet occurring in Colorado agricultural, and industrial sources can affect trout and and Kansas, as were giant salvinia (Salvinia molesta) other aquatic biota (Crisp 1993). for Colorado, rusty crayfish for Kansas, New Zealand mudsnail for Kansas and South Dakota, quagga v Organic materials such as domestic sewage, from Colorado and Wyoming, and round goby farm slurry, silage liquor, and various (Neogobius melanostomus) and (Gymnocephalus industrial effluents create high demand cernuus) from Kansas. for microbial oxygen; this in turn depletes dissolved oxygen levels in the water, which Of the 29 species listed, only one might be stresses fish and may be lethal. viewed as a success story for control. The rusty crayfish was introduced into a Wyoming pond, but v Increases in suspended solids can influence it was subsequently removed by state officials at the fish at all stages: redds can be choked by considerable cost to both the state and the company that the silt; if interstices are filled, alevins cannot imported the prohibited species (http://gf.state.wy.us/ “swim up” and are asphyxiated; suspended downloads/pdf/RegionalNews/RKrustycrayfish.pdf). solids and silt affect the sight-feeding However, considerable effort at both state and federal ability of rainbow trout and can abrade gill levels is being directed at public education about membranes. particularly vagile and (e.g., Eurasian watermilfoil (Myriophyllum spicatum), zebra mussel v Toxic materials found in effluent can poison (Dreissena polymorpha), round goby (Neogobius fish or result in high oxygen demand, but they melanostomus)), how to identify them and how to can also affect fish indirectly through their control their accidental spread (see websites for: USDA effects on suspended solids and siltation. National Invasive Species Information Center, http: //www.invasivespeciesinfo.gov/; USGS Nonindigenous v Inorganic and other nutrients Aquatic Species program, http://nas.er.usgs.gov/; US commonly wash off the land in large Fish and Wildlife Service Aquatic Nuisance Species quantities, result in program, http://www.fws.gov/Contaminants/ANS/ (enrichment) of streams, and can support ANSContacts.cfm; the 100th meridian initiative, http: growth of toxic blue-green algae in lake //www.100thmeridian.org/; the intergovernmental environments; effluent discharge may be Aquatic Nuisance Species Task Force, http:// consistent and or sporadic and result in drastic www.anstaskforce.gov/default.php). impacts on food availability for fish.

44 45 v Effluent can have drastic effects on pH, which densities leading to supplemental stocking. Such fishing in turn may alter animal physiology, solubility pressures can dilute the benefits of other management of organic and inorganic compounds, and actions set in place to increase trout biomass. other aspects of ecosystem function. Although it may sound like a non sequitur, even v Heated effluent affects water temperature, catch-and-release practices may result in excessive altering dissolved oxygen concentrations in harvest. For example, in catch-and-release waters, the receiving waters. individual Yellowstone cutthroat trout may be captured multiple times (Kershner et al 1997). While catch- v Concern is growing rapidly over endocrine and-release clearly reduces immediate mortality, each disruptors in effluent from population centers capture, handling, and release event generates stress and (Gray et al. 2000); such compounds trace increases susceptibility to a variety of other factors that to a variety of drugs used for birth control may lower vitality or survival and thereby functionally and other purposes, are active at very low generate harvest beyond what is immediately obvious. concentrations (making detection difficult), Bartholomew and Bohnsack (2005) calculated an and may affect animal maturation average 20 percent post-release mortality for rainbow and gender and thereby influence the potential trout, but estimate this would rise to roughly 50 percent for successful spawning in fish and with three catch-and-release events and to near 70 populations. percent with five such events. Initial surprise at such high mortality figures declines in light of Meka’s (2004) Dams demonstrations of the effects of hook structure, landing time, and angler experience on structural damage to Dams cause discontinuities in stream and river rainbow trout in a catch-and-release system. Meka and systems, thereby changing long- and short-term stream McCormick (2005) also described significant, sublethal discharge patterns and permanently altering riverine physiological responses to these same variables. ecosystems. These discontinuities disrupt gene flow among previously interbreeding populations, setting the Changes in water temperature stage for loss of genetic diversity through selection and drift, and interfere with or eliminate movements within Changes in water temperature may exert the system, especially dispersal of young fish and particularly strong impacts on fishes in thermally well- migration to feeding or spawning sites (Gillette et al. mixed stream environments (Myrick 1999, Myrick and 2005). Ecological conditions in reservoirs behind dams Cech 2000). At present, short-term changes often result are unlike those to which stream fishes are adapted, but from natural or anthropogenic reductions in stream flow they do meet habitat and spawning requirements of a or reduction of riparian canopies that lead to more rapid wide array of often predatory fishes adapted to standing and extensive warming or cooling depending on the or slowly flowing waters. Failure of natural reproduction season. Contributors to these changes include drought, in trout populations influenced by dams may require water withdrawals, dam operations, and a variety of hatchery introductions to support sport fisheries. These near-stream development activities. effects are most obvious, if not most pronounced, in the Columbia River, where salmon abundance is 5 Present-day managers, however, must address to 10 percent of pre-dam levels due to loss of habitat likely long-term effects of increasing temperatures. and access to spawning sites, increased mortality of Predictions relevant to how global warming may affect migrating smolts in reservoirs and dam turbines, and Region 2 states include (Glick 2006, U.S. Environmental reliance on hatchery fish to support fisheries (Behnke Protection Agency 2008): 1998). Dams are common in Region 2 states; in fact, Kansas has the second highest number of dams in the v Increased atmospheric temperature will United States (Gillette et al. 2005). increase frequency of drought and fires, increase evaporation, and change precipitation Excessive harvest patterns.

Some declines of rainbow trout in healthy fisheries v Heavier precipitation in some areas will have been associated with over-harvest (Everett 1973, increase risks of flooding, expand floodplains, Binns 2004), including depletion of stocks of naturally increase variability of stream flow, increase reproducing rainbow trout in Region 2, with lower fish velocity during high flow periods, increase 46 47 erosion, and reduce water quality and aquatic by states is for 2000 (USGS 2008). Specific usages system health. identified in this state-by-state report include public supply (i.e., water released to public or private water v Droughts, changing patterns of precipitation suppliers who then pass it on to a variety of users), and snowmelt, and increased evaporation domestic, irrigation, livestock, aquaculture, industrial, will change availability of water for drinking, mining, and thermoelectric power. and may result in increased competition for water from agriculture, industry, and energy The doctrine of prior appropriation (also production sectors. “Colorado Doctrine”) drives water rights in the western states. This doctrine states that while no person v Altered precipitation and reduced snowpack may own the water, individuals, municipalities, and will change hydrographs (e.g., timing of corporations may use it for beneficial purposes (state peak flows, available water) and thus change details below). This prior appropriation system allows water flow to and size of lakes, streams, and water users to construct works in arid regions to move wetlands. water over long distances to where the water is needed and provides for assignment of a water use priority date. v As waters warm, existing species will be Since the investment to construct works to move water replaced by species adapted to the warmer long distances is considerable, it was and continues water, disrupting aquatic system health and to be important to protect that investment. The first to allowing non-indigenous and/or invasive use (appropriate) the water establishes a water right by species to become established, with diverting water and putting it to a beneficial use; this particularly severe impacts on high-elevation, first use provides the user with the senior water right. coldwater species. During periods of low water availability, senior rights take precedent over any junior rights and must be fully v Warmer waters will make hypoxia more satisfied before junior rights are met. This and the early common, foster harmful algal blooms, and view that “beneficial uses” meant domestic, municipal, change the of some pollutants. agricultural, or industrial uses led to needs for recreation and wildlife being relegated to very weak positions. All Managers should view these concerns and Region 2 states adhere to this doctrine. predictions as relevant to planning now. Consider quotes from Field et al. (2007) in the Environmental Colorado: Colorado surface water law Protection Agency report: “...[s]pring and summer (State Constitution, Article XVI, and Colorado snow cover has decreased in the U.S. west...,” “...[t]he Revised Statutes) is based upon the doctrine of prior fraction of annual precipitation falling as rain (rather appropriation or “first in time - first in right”, and than snow) increased at 74% of the weather stations the priority date is established by the date the water studied in the western mountains of the U.S. from 1949 was first put to a beneficial use. A modified formof to 2004...,” “[t]hreats to reliable supply are complicated prior appropriation governs the establishment and by the high population growth rates in western states administration of groundwater rights (Ground Water where many water resources are at or approaching full Management Act of 1965). What constitutes beneficial utili[z]ation...,” and “...streamflow has decreased by use in Colorado is not specified in statute, but previous about 2% per decade in the central Rocky Mountain categories have included natural resource uses such as region over the last century.” Although somewhat Aesthetics and Preservation of Natural Environments, dated, conservative estimates by O’Neal (2002; based Fisheries, Minimum Flow, Recreation, Wildlife on several modeled scenarios for continued global Watering and Wildlife Habitat. [Source: Bureau of Land warming) suggest loss of 4 to 20 percent of trout and Management, National Science and Technology Center, salmon habitat by 2030, 7 to 31 percent by 2060, and Western States Water Laws, Colorado Water Rights 14 to 36 percent by 2090, depending on fish species Fact Sheet, http://www.blm.gov/nstc/WaterLaws/ and model. colorado.html.]

Outdated water rights systems Kansas: Kansas is a “prior appropriation state” in regard to water rights, as spelled out in the state’s Competition for water can be intense, particularly water appropriation act (KSA 82a-701). It has been in many of the western states. At the time of this illegal since 1978 to use water for any purpose, other publication, the most recent summary of water usage than domestic use, without either holding a vested right 46 47 or receiving a permit to appropriate water from the retention of sufficient water in waterways to support Division of Water Resources. This applies to ground normal aquatic ecosystem functions. Water allocations and surface water on both private and public property. are the purview of the states, which differ in the agencies [Source: Northwest Kansas Groundwater Management allocating water rights, acceptance and support of District No. 4, http://www.gmd4.org/law.html; also, instream flow allocations, and approaches to allocation http://www.ksda.gov.] of ground water vs. surface water (Tellman no date).

Nebraska: The State of Nebraska Constitution v The Colorado Water Conservation Board (Article XV-6: Right to divert unappropriated waters) oversees the instream flow program in establishes the doctrine of prior appropriation as Colorado, and acquires instream flow rights the primary determinant of water rights. The Article through either a new application process or specifies that highest priority is given to “domestic by acquiring established, senior water rights purposes,” followed by “agricultural purposes” and (Merriman and Janicki no date). They also subsequently “manufacturing purposes.” Of relevance have an active instream flow monitoring to fisheries managers is an associated Annotation and protection program for established (5. Miscellaneous) that notes the term “divert” does water rights. Groundwater and surface water not prohibit nondiversionary appropriations, such as allocation systems are integrated so that instream flow uses. impacts on one type of water may affect granting of rights to another type of water South Dakota: The Dakota territorial legislature (Tellman no date). Water rights may be bought enacted legislation in 1881 establishing a procedure to and sold. Where there is no unappropriated “locate” surface water rights, and later (1907) the state water, this system makes room for newcomers legislature affirmed the doctrine of prior appropriation. without harming previous rights holders. In 1955, legislation made use of ground water also subject to the doctrine of prior appropriation. [Source: v Kansas water use is directed by the Kansas South Dakota – Department of Environment and Natural Water Plan, developed by the Kansas Water Resources, http://www.state.sd.us/denr/des/waterrights/ Office and approved by the Kansas Water wr_history.htm.] Authority. The state defines minimum desirable streamflows, and the Chief Engineer Wyoming: Wyoming’s first surface water laws withholds from appropriation that amount of were enacted in 1875, and more comprehensive laws water needed to maintain minimum desirable were adopted along with the state constitution in 1890 streamflow (K.S.A. 82a-703(b)). The state (Jacobs et al. 2003). Water rights in Wyoming, as in also can limit permitted withdrawals to most of the western states, are regulated by priority and ensure that environmental flow needs are based on the “doctrine of prior appropriation.” Preferred met even in times of drought, and can uses of both surface and ground water, in order, are (1) purchase water rights on over-appropriated drinking water for both humans and livestock, (2) water waterways in order to establish minimum for municipal purposes, (3) water for steam engines environmental flows. Kansas has a unified and general railway use; water for cooking, laundering, water appropriation system. Permit approval bathing, and refrigerating (including the manufacturing in certain areas is subject to minimum of ice); water for steam and hot-water heating plants, streamflow requirements. steam power plants, and (4) water for industrial purposes (Jacobs et al. 2003). v Nebraska’s instream flow law, overseen by their Department of Natural Resources, Instream flow is among the most restrictive in the West (Zellmer no date). Instream flow waters As human populations and the volume and must come from unappropriated sources, complexity of their demands grow, concerns over inhibiting sources from donations or the availability of water for aquatic systems and the purchase. Unappropriated water must be recreational benefits they provide also grow (see available to provide the approved flow at Gillilan and Brown 1997 for background; Brown 2003). least 20 percent of the time. Only the Game The response by resource management agencies has and Parks Commission and 23 Natural been to seek “instream flow” rights and allocations Resource Districts (no individuals) may own that guarantee, or at least increase the likelihood of, an instream flow right. Instream flows may 48 49 be appropriated “to maintain the existing water separately, but explicitly integrates recreational uses or needs of existing fish them in the allocation process (Tellman no and wildlife species,” and so may not cover date). The presumption is that waters are not enhancements. Finally, an instream flow may connected unless proven otherwise. only be granted if the demonstrated benefit outweighs economic and social considerations Fish stocking in wilderness and other protected (e.g., recharge for municipal water systems, areas water quality maintenance, etc.). Individuals may change the purpose of their water right Of the five Region 2 states, only Kansas has no to instream flows, but fear of losing a water land designated as wilderness, and only two wilderness right to the state may deter such conversions. areas occur in each of Nebraska (12,429 acres; 0.03 Nebraska is the only Region 2 state to treat percent of state acreage) and South Dakota (77,570 groundwater and surface water as legally acres; 0.16 percent state acreage; see wilderness.net separate systems (Tellman no date). for statistics and maps). Nonetheless, anglers fish for rainbow trout in Soldier Creek, Soldier Creek v South Dakota does not appear to have a Wilderness Area, Nebraska National Forest, and in specific instream flow program, but has South Dakota’s Black Hills National Forest, which approved water rights for what amounts to encompasses the Black Elk Wilderness Area. In instream flow on several occasions (Gillilan contrast, each of Colorado and Wyoming contain more and Brown 1997). Among the types of uses than 3 million acres of wilderness that constitutes requiring a permit are “Recreation use” more than 5 percent of the land area in each state, and “Fish and wildlife propagation” (http: predictably focused on high altitude sections of the //www.state.sd.us/denr/des/waterrights/wr_ . The USFS administers all of the permit.htm); while the term “propagation” wilderness area in Wyoming and roughly 93 percent is somewhat unusual in this context, these of the wilderness acreage in Colorado; the remainder recognized uses should cover instream flow is administered by the BLM, the National Park Service, needs. Permits for water use are reviewed and the U.S. Fish and Wildlife Service. and awarded by the Water Management Board and Chief Engineer, South Dakota Because relatively few fishes colonized mountain Department of Environment and Natural watersheds of the western United States after the last Resources, and while they operate separate glaciation, approximately 95 percent of roughly 16,000 groundwater and surface water allocation high elevation lakes were historically fishless. Native systems, they explicitly unify criteria and and nonnative sport fish have been introduced into priorities for allocation. many historically fishless lakes in these areas (over 60 percent of these high mountain lakes have been v Wyoming has been assessing and acquiring stocked; Pilliod and Peterson 2001), creating conflicts instream flow allocations for more than 30 between managing natural ecosystems and providing years, and is presently working under the opportunities for recreation (Knapp et al. 2001, Wiley guidance of a 5-year water management 2003b). Such conflicts grow naturally from state desires plan (Annear and Dey 2006). The Game and to develop, expand, and manage remote or wilderness Fish Department selects stream segments fisheries (section 4(d)(8) of the 1964 Wilderness on which to file for a right. The Water Act; P.L 88-577) and federal mandates to protect the Development Commission then applies for biological integrity of wilderness (Pilliod and Peterson the appropriation following a hydrologic 2001, Wiley 2003b, USDA Forest Service 2007). study to determine if instream flow can For example, the USFS policy regarding fisheries be provided from unappropriated natural management in wilderness specifies no stocking of flow of the stream or if storage water will exotic species and places highest priority for stocking be needed for part or all of the instream on Federal threatened or endangered indigenous species use. That study is supplied to the State (species occurring naturally in the area), followed Engineer, who conducts a public hearing in order by other indigenous species, threatened or and decides whether to approve, approve endangered native (to the United States) species, and with modifications, or reject the application. other native species. These guidelines relegate rainbow Wyoming regulates groundwater and surface trout to the lowest priority category.

48 49 Another policy (USDA Forest Service 2007) they are more vulnerable to predators and less able directs the USFS to “stock barren waters only after to compete for food. Flushing flows, if they occur or determining that the scientific and research values can be produced from reservoir releases, can clean of such barren waters will not be eliminated from substrates of accumulated silt and provide habitat for a wilderness...” Fish introductions into previously macroinvertebrate prey of trout. fishless lakes have affected lake nutrient cycling, algal dynamics, and the invertebrate fauna, and in many areas Fire these introductions have caused declines in resident (Knapp et al. 2001). However, many of Recent large and sometimes catastrophic fires in these effects followed establishment of self-sustaining the western states, including some in Region 2, have populations stocked before wilderness-related concerns attracted considerable public concern over the effects arose (Wiley 2003b). In any event, once likely effects of on land, timber, terrestrial wildlife, structures, and fish stocking have been identified within a wilderness, human life. Clearly, decades of fire suppression have managers should be able to target specific lakes for contributed to the frequency and severity of such fires protection or restoration without overly compromising (Donovan and Brown 2007). The less easily observed fishing opportunities in remote and environmentally inhabitants of aquatic systems receive less attention, pristine areas (Pilliod and Peterson 2001). yet aquatic ecosystems often suffer severe post- fire impacts. Natural disturbance Fire is common in the Rocky Mountain area Drought in general (Table 11) and sufficiently common in all Region 2 states to suggest potentially widespread Low flows significantly alter and limit trout impact on virtually any waters in those states. This is habitat in streams. In addition, low flows deposit particularly evident from a map of wildfire danger in the silt, fill interstices between rocks and gravel, and United States (Figure 7). In 2005 alone, for example, limit availability of invertebrate foods for trout, there were 28 large fires (≥ 100 acres in timber, ≥ thus influencing both wild and stocked fish. During 300 acres in grasslands, or fire with Type 1 or Type 2 drought, juvenile habitat is often reduced significantly, Incident Management Team assigned) in Colorado, 16 forcing these fish to occupy adult habitats where in Kansas, one in Nebraska, seven in South Dakota,

Table 11. Federal and non-Federal fires in the Rocky Mountain area, 2007. Human Lightning WFU* Total Agency Type Agency Fires Acres Fires Acres Fires Acres Fires Acres Federal BIA 920 27,646 187 2,139 0 0 1,107 29,785 BLM 73 1,687 531 15,264 8 121 612 17,072 FWS 15 1,598 7 133 0 0 22 1,731 NPS 8 308 28 9 2 1 38 318 USFS 154 411 367 43,132 10 107 531 43,650 State CO 1,706 9,562 1,226 8,524 0 0 2,932 18,086 KS 2,440 24,835 112 1,672 0 0 2,552 26,507 NE 687 7,826 114 12,475 0 0 801 20,301 SD 520 27,305 507 153,094 0 0 1,027 180,399 WY 364 14,457 233 14,602 0 0 597 29,059 Other Other 4 3,533 1 0 0 0 4 3,533 RMA Total Total 6,891 119,168 3,313 251,044 20 229 10,223 370,441 Fires occurring on Federal agency lands are listed only for those agencies. State figures represent all Non-federal fires in the respective state (as reported to the USFS Regional Office’s State and Private Forestry staff). WFU* - Wildland Fire Used for Resource Benefit - naturally ignited fires managed to accomplish specific pre-stated resource management objectives in predefined geographic areas outlined in Fire Management Plans. Data for WFU fires are not included in columns for lightning- caused fires. Source: Rocky Mountain Area and Coordination Center 2007 Annual Report, National Interagency Fire Center, Boise, Idaho.

50 51 15 days, ending 2008Jun 29 30 days, ending 2008Jun29

Figure 7. Fire threats and drought in the western United States. Upper panels: forecast fire danger class for (A) 25 May 2006 and (B) 7 July 2008. Light green areas indicate Moderate danger; yellow, orange and red indicate High, Very High and Extreme danger, respectively. Lower panels: Drought conditions in the 48 contiguous states, averaged over 15- and 30-day periods in June 2008. Source: Rocky Mountain Area Coordination Center of the National Interagency Fire Center, Boise, Idaho (fire danger maps are updated daily).

and nine in Wyoming (total 61; Rocky Mountain Area reduce fire danger may exert negative impacts on local and Coordination Center, 2005 Annual Report, of the stream systems. National Interagency Fire Center, Boise, Idaho). Species with narrow habitat requirements that Aquatic resource managers should take active occur in fragmented populations or in highly degraded interest in all stages of response to potential or real fire. or lower order (e.g., 1st and 2nd order) systems are Personnel of Region 2 continue to treat forests to reduce probably most vulnerable to fire and fire-related fire danger, including mechanical removal of fuels, disturbance. However, fishes demonstrably affected prescribed burns, and control of naturally ignited fires by wildfire in the southwestern United States from in ways that meet existing fire management objectives. 1989-2003 included five non-natives (brook, brown, Such labor intensive and expensive programs are and rainbow trout, green sunfish, yellow bullhead) and long-term efforts; in FY 2005, Region 2 treated 13 natives (, three suckers, and nine cyprinid 149,486 acres, 57 percent (85,691 acres) of which minnows) representing an array of habitat requirements were in wildland-urban interface zones (USDA Forest and abundances (Rinne 2004). Service Region 2 Fiscal Year 2005 Fuels Treatment Accomplishment Report, February 2006). Fire should Immediate effects of fire may include potentially therefore be considered a potential threat to almost any lethal increases in water temperature, particularly in aquatic system beyond urban areas. Even methods to small, shallow waters exposed to severe fire conditions. 50 51 Hitt and others (2003), cited in Cilimburg and Short raises resistance to scouring; loosening of the bed 2005) reported an 8-hr period where water temperatures during spawning may lower this same resistance. Long were 14 ºC greater than in a nearby unburned stream. interludes between storm events also enhance stability Similarly, changes in water chemistry may include of the bed. Activities and events that can destabilize the large spikes in nitrate, phosphate, and ammonium due and lead to severe and chronic scour include to diffusion of smoke into stream water and ash inputs removal or displacement of large woody debris due (Cilimburg and Short 2005). If water temperatures to stream clean out after logging, urban development, rise, oxygen levels are also likely to drop. Fish kills removal of debris jams to improve fish passage, and are not uncommon. floods or debris flows. Other factors that increase the likelihood or severity of scour include increased storm There are longer term impacts as well (Cilimburg water runoff from impervious surfaces associated with and Short 2005). Temperatures in smaller streams may urban development, timber harvest in areas susceptible remain unusually high if the riparian and forest canopy to rain-on-snow runoff events, increased supply of has been removed. Flow volume invariably increases, coarse sediment due to upstream landslides, and stream particularly in areas with steep terrain, and may lead channelization projects. Timber harvest, roads, mining to restructuring of stream substrata and changes in operations, and urban development accelerate erosion, normal seasonal patterns of discharge. Debris, ash, and stream side vegetation is sometimes removed or and other sediment inputs increase, with the potential disturbed by timber harvest, urban development, and for increased turbidity, lower primary productivity, agriculture, and grazing operations. and suffocation. Fish that survive may move from the affected areas to avoid chemical and other alterations Predation to their habitat (Cilimburg and Short 2005). Debris flows following an Arizona fire created new barriers As noted above, rainbow trout are targets of a to fish movements (Rinne and Carter 2002), potentially wide array of predators. Williams and others (1997) inhibiting recolonization of affected stream reaches. documented rainbow trout susceptibility to predation by a large bull trout population in the lower and Lake The USFS commonly employs timber harvest Billy Chinook (Williams et al. 1997). Cutthroat trout projects in areas struck by fires. These efforts allow are believed to provide a key food source for at least for the economical recovery of the burned timber, 28 species of birds and mammals (Williams 2002). provide work for nearby communities, and accelerate In Yellowstone National Park, a team of researches restoration of forest vegetation within the burned areas. followed a sow bear with cubs and concluded they Nonetheless, these efforts actually slow forest recovery averaged 100 fish per day for 10 days. It is futher (Karr et al. 2004) through compaction and chemical believed that pelicans in Yellowstone National Park get alteration of soils, removal of organic and inorganic the majority of their nourishment from cutthroat trout, nutrients, increasing erosion and stream sedimentation, consuming as many as 300,000 pounds in a season. eliminating shade trees for regenerating plants, etc. Cormorants and pelicans greatly increased their take of trout after 10 to 16 cm fish were stocked in the North Scour (extracted from Schuett-Hames et al. Platte River, Wyoming, and they may have taken up to 1996) 80 percent of trout stocked in 1994 (Derby and Lovvorn 1997, Lovvorn et al. 1999). Developing eggs and alevins of rainbow trout are vulnerable to scouring that causes mechanical shock, Such reports focus on later life history stages crushing, entrainment of the fish with moving gravel, (fingerlings and larger) of rainbow trout and other or release of eggs and larvae into above-substrate salmonids, but managers should also consider sources current. Both biological and physical factors affect of predation on the eggs and fry. Both round goby the vulnerability of redds to scour. Large females tend (Neogobius melanostomus; listed as a potential to deposit eggs at greater depth than do smaller fish, nuisance species by Kansas, but not recorded from reducing the probability of scour. Spring-incubating Region 2 yet) and sculpins (Cottus spp.; residents salmonids, such as most rainbow and cutthroat trout, are in all Region 2 states) penetrate interstitial spaces vulnerable where snow melt produces peak flows in late in cobble and gravel redds to prey on salmonid eggs spring or early summer, but late fall or winter rainfall and fry (Chotkowski and Marsden 1999, Jonas et al. will be particularly damaging to winter-incubating 2005). Salmonid eggs may be particularly sensitive to populations of rainbow trout. Construction of redds attack immediately following spawning, as the female removes smaller particles, coarsens the substrate, and covers the redd; mature male Atlantic salmon parr feed 52 53 actively on just-spawned eggs (Montgomery et al. Rainbow and native fishes 1987). Invertebrates may also be threats to eggs and sac fry. Brown and Diamond (1984) described predqation Since their introduction into waters outside their on rainbow trout eggs by two stoneflies (Plecoptera), a native range, rainbow trout have displaced native species phantom crane (Diptera), a caddisfly (Trichoptera), in Region 2 and elsewhere from their historic range by and a gammarid amphipod. means of competition, predation, and other detrimental influences, including hybridization and introgression Management of Rainbow Trout in (Ross 1997). Pritchard and Crowley (2006) identify Region 2 the primary threat to long-term persistence of Rio Grande cutthroat trout as the presence of non-native Implications and potential conservation trout. Non-native trout, particularly rainbow trout, are elements either stocked or occur in self-sustaining populations in the majority of waters that historically supported Rio Rainbow trout are not presently of conservation Grande cutthroat trout. concern, but various populations may ultimately suffer environmental, anthropogenic, and political threats. Kruse et al. (2000) surveyed most of the Long-term drought cycles, perhaps amplified by global streams that might harbor Yellowstone cutthroat trout warming, may reduce volume and consistency of flow in outside Yellowstone National Park. Genetically pure stream systems and potentially lead to warming of water Yellowstone cutthroat trout occupied only 27 (26 in reservoirs or lakes. While acquisition of primary percent) of 104 streams surveyed, and only 30 percent water rights to maintain stream flow is advisable, of 822 km of the perennial streams that contained trout. history suggests that costs would be considerable and Henderson et al. (2000) tracked spawning movements competition from extraction-dependent users would of rainbow, Yellowstone cutthroat, and rainbow- be intense. Populations of greatest value should be Yellowstone cutthroat hybrid trout in the South Fork identified, and alternative approaches to maintaining Snake River, and they discovered considerable spatial water supply to those populations should be explored. and temporal overlap of spawning sites in rainbow and Yellowstone cutthroat trout. Hybrid trout genes Human population expansion, accompanied by surveyed were dominated (64 percent) by rainbow destructive development of land, is inevitable. Region trout markers. 2 personnel should be integrally involved, where possible, in planning for development in areas around, Colorado River cutthroat trout were historically and particularly upstream, of National Forest System common in the upper Green River and Colorado River lands. Riparian corridors and forest buffers along watersheds, but they now occupy less than 1 percent streams should reduce sediment and pollutant inputs of their previous range. However, the amount of this from building and roads that would do damage locally restriction due to rainbow trout versus brook trout or and downstream. Such protections could well enhance other fishes is unclear. Special management status for property values if accompanied by educational efforts this fish has been sought in Colorado, Wyoming, and explaining their importance to stream ecology and Utah (Kershner et al. 1997). emphasizing that enhanced biodiversity contributes to the “living-near-nature” experience. Outside of Region 2, the westslope cutthroat trout (Oncorhyncus clarki lewisi) occupies less than 5 The major political threat to persistence of some percent of its historic range within the upper Missouri rainbow trout populations appears to be mandates River drainage in Montana (Shepard et al. 1997), and associated with the ESA and related legislation at hybridization and introgression are well-established state or federal levels. Native fishes in the arid western between coastal cutthroat trout and anadromous United States have a dismal record of recovery even rainbow trout (Young et al. 2001). Perhaps the most after responsible agencies have committed tremendous disturbing development in the widespread concerns energy and resources to recovery efforts. Rainbow over interactions of rainbow trout with cutthroat trout trout are implicated as contributors to declines of focuses on Colorado’s greenback cutthroat trout. native species, and their removal from designated Originally listed as Federally Endangered, this fish critical habitat for native fishes will certainly appear was downlisted to Threatened status and eventually in recovery plans for a variety of salmonid and non- considered for removal from listing on the basis salmonid species. This threat may grow as additional of dedicated and extensive recovery efforts by the species are listed at national and state levels. Colorado Division of Wildlife to establish naturally 52 53 reproducing populations. Recently, however, Metcalf et see greater use with the many native fishes of the West al. (2007) reported molecular evidence demonstrating for which there is concern. Nonetheless, to meet the that many of the putative pure strains of greenback trout needs of management, rainbow trout must be subject developed through Colorado Division of Wildlife efforts to population and, as more self-sustaining populations were actually descendents of Colorado River cutthroat are developed, demographic monitoring and analyses. trout stocked a century ago. Metcalf et al. (2008) Habitat, including concerns about instream flow during recently demonstrated hybridization between rainbow critical periods, remains an issue as well. Habitat quality trout and greenback cutthroat trout and Colorado River indices based on readily measured habitat variables cutthroat trout populations. It appears that greenback may simplify rapid evaluation of existing habitat over trout populations are a greater cause for concern than the range of the trout, as long as they take habitat previously thought. requirements of all life stages into account.

Hybridization may also be a threat facing some Rainbow trout as a Management Indicator populations of westslope cutthroat trout (Hitt et al. 2003). Species Westslope cutthroat trout and rainbow trout naturally occur in sympatry over a portion of their ranges (Figure Ecosystem management has become a driving 1), so reproductive isolating mechanisms likely evolved concept underlying natural resource management between the two species in these areas. Consistent with in the United States. Ideally, population and habitat that expectation, hybridization between the two species monitoring of many species within an ecosystem is thought to be rare, but small amounts of introgression over extended periods would provide managers with are detectable by molecular genetic methods. indications of ecosystem health. Such time- and labor- intensive study is, however, beyond the capability of Campton and Kaeding (2005) recently commented existing state or federal programs. Faced with such on a recommendation that only “nonhybridized” constraints, responsible agencies often monitor the fate populations be considered for protection under the of one or a few species that may be indicators of the Endangered Species Act (ESA). They note that any health of an ecosystem or species of concern (“target population with detectable traces of introgression would species” below). be excluded from ESA and eligible for eradication, and they point out a biological dichotomy between “(1) the Selection of such Management Indicator Species need to conserve the genetic resources of an imperiled (MIS) has been directed and guided by the National species in which introgression has occurred and (2) Forest Management Act of 1976 (NFMA; as amended the need to eliminate hybridization threats posed by in several subsequent years). Population dynamics introduced taxa.” In their response to Campton and of such species are expected to reflect the effects of Kaeding (2005), Allendorf et al. (2005) defined a management activities on important members of a nonhybridized or pure population as one having less given biota. The NMFA recognizes that MIS may be than 1 percent introgression with either rainbow trout drawn from: or any other subspecies of cutthroat trout, and urged that policies and guidelines should be developed on a v endangered and threatened plant and animal species-by-species case. They concluded that USFWS species, has two opposing policies for dealing with hybridized populations of cutthroat trout, and that the USFWS is v species with special habitat needs that may be not relying on the best data available to address the influenced by management activities, threat of hybridization to westslope cutthroat trout (Allendorf et al. 2005). This concern is certainly not v commonly hunted, fished, or trapped species, restricted to westslope cutthroat trout. Of the 14 named and unnamed cutthroat subspecies, two are extinct while v non-game species of special interest, and other species are of special concern (Williams 2002). v other plants or animals selected because their Tools and practices population dynamics may indicate effects of management activities on other species or on A wide array of methods exists for managing water quality. populations of salmonid fishes (see review in Pritchard and Cowley 2005), especially rainbow trout. Some Implicit in the concept of indicator species is methods (e.g., extensive genetic analysis) are likely to that indicator dynamics reflect dynamics of other 54 55 ecologically similar species (e.g., guild members), v large populations allow sacrifice of individuals and habitat of the indicator species should overlap for physiological or compositional testing extensively with those of all other guild members that might indicate elevated stress (e.g., stress (Block et al. 1987). hormones) or other indicators of declining health (e.g., low lipid levels) not evident from There remains considerable concern over the simple length/weight measurements; validity and utility of use of MIS as predictors of ecosystem responses and over how they should be v rainbow trout are likely to be more available selected. At least three categories of indicator species for relevant experimental manipulations in have emerged, functions of which should be considered laboratory and field to elucidate relationships as Region 2 National Forests and Grasslands develop between types and intensity of environmental or modify their own lists of indicators. The term disturbance and demographic changes; “indicator species” is applied to species used to assess the magnitude of anthropogenic disturbance (ecosystem v rainbow trout are widespread in Region 2, so health), to monitor population trends in other species, an initial assessment of the effects of various and to locate areas of high regional biodiversity (Caro environmental conditions may be achieved and O’Doherty 1999, Caro 2000). “Umbrella species” rapidly through comparisons among locations describes those used to delineate the type of habitat or differing in key environmental variables. size of area for protection; these are often species with large home ranges that encompass larger populations Cons: of species with small home ranges. “Flagship species” are those species used to attract public attention, raise v one reason rainbow trout are widely awareness, or attract funding to a conservation cause. successful is their ability to tolerate varied Despite the NFMA focus on indicator species, each of environmental conditions; sensitive target these functions will be important to National Forest species could easily be harmed or lost before System lands. managers could detect a response to changing conditions in rainbow trout populations; Should rainbow trout be used as MIS in Region 2? The answer may vary among forests and grasslands, v relatively slow development and maturation and likely among locations within individual rates, relatively low fecundity, and sufficient jurisdictions, for utility of the trout as an indicator must mobility to allow relatively long distance be related to explicitly defined criteria that are in accord avoidance movements may make vertebrate with assessment goals (Landres et al. 1988). There are animals less useful for detecting the influence both pros and cons to use of rainbow trout as MIS in of environmental degradation than non- Region 2 (partial lists; based in part on Landes et al. vertebrate organisms; 1988, Caro and O’Doherty 1999, Caro 2000, Caro et al. 2005), including: v ideally, responses of indicator and target species should be similar, but data Pros: demonstrating this relationship are difficult to acquire, particularly when conditions differ v rainbow trout are not of special concern in among communities at different locations; Region 2 states, so permitting requirements for research and monitoring should be less v demographic parameters are likely to vary stringent than with listed target species; considerably among populations of rainbow trout based on origin of the population v rainbow trout are frequently common, (e.g., recently stocked vs. established), allowing large samples to be collected identity of the strain, pure vs. hybrid, etc.; for monitoring studies, with associated such will either demand many studies to reductions in error for estimated population demonstrate similar responses of indicator sizes and length/weight relationships, as well and target species or will reduce the accuracy as more robust data across different size and of predictions of response at one location life history classes; when the indicator-target relationship was developed at another location;

54 55 v environmental change may exert either programs that inform about the native species, density-dependent or -independent effects; declining populations, management efforts, and in either case, small or isolated populations related topics. of target species are likely to suffer genetic and other effects more severely than large or Mixed-species fisheries (1c) provide another widely-connected populations of indicator somewhat unusual consumptive use and species. educational opportunity, but with less constraining habitat conditions that may allow better fishery Landres et al. (1988) suggest that reliance on a returns per unit time. MIS should occur only when other assessment options are unavailable. Implicit in this recommendation is the Finally, exclusive or near-exclusive dependence suggestion that such reliance should be considered on rainbow trout (1d) may be required to support a transitional step. As information grows about more intensive fisheries or those in degraded community composition and function and the biology habitat. The ecological flexibility of rainbow trout of individual species within that community, capability and readily available public and private hatchery to model community and ecosystem responses more systems combine to make rainbow trout the ideal precisely will grow. coldwater fish to support a wide array of sport fishing demands not met by more constraining Management approaches conditions involving native species.

Rainbow trout must be viewed as permanent 2. Evaluate and improve habitat, as necessary, so residents of Region 2 ponds, lakes, streams, and rivers. that it will support habitat requirements of all Unfortunately, a continuing management conflict pits trout life history stages (see Habitat section their negative impacts on native species against their above). If self-reproducing populations can widespread acceptance as a sport and food fish. Clearly, be established through habitat improvement, none of the following tactics will fit all habitats and it will reduce costs associated with stocking desires, and habitat or fish population manipulations or allow limited hatchery resources to be will always take place against a backdrop of constituent, directed to fisheries that require stocking. agency, and governmental demands and conditions. 3. Where stocking of rainbow trout is required 1. Identify locations best suited for at least four (e.g., ponds in Cimarron National Grassland, management approaches: irrigation canals, some reservoirs), identify a. complete protection (no take) of native genetic strains with the best performance for species in their historically native habitat conditions in the area targeted for stocking. b. native-only sport fisheries c. mixed native/rainbow trout fisheries 4. Consider isolating species, subspecies, d. moderate to high intensity rainbow trout and strains from gene exchange with other fisheries. groups. For example, native-only populations restricted to headwater streams above Areas of complete protection (1a) serve, in part, natural or artificial barriers to upstream as sources of species-specific genetic diversity movement would be protected against and essentially pure stocks for reestablishing or natural colonization from below, but could supplementing native fish populations. This is nonetheless contribute juveniles to fisheries particularly likely if a population is sufficiently in areas downstream. Where some natural large to avoid loss of genetic diversity from reproduction occurs, similar isolation of genetic drift and if native habitat is sufficiently specific strains of rainbow trout that perform healthy to avoid unusual selection pressures. particularly well under local environmental or fishery conditions may help to retain desired Areas open to native-only sport fishing (1b) characteristics for longer periods than if they provide another repository of genetic diversity, were mixed with other rainbow trout strains and they have the potential to attract anglers or potentially hybridizing species. interested in an unusual fish and an unusual sport fishing experience. Such programs 5. Consider developing the most productive should be supplemented with public education (to the angler) fishing opportunities at points 56 57 closest to primary access, and accompany more substantive projects. These products those efforts with improved support facilities could be downloaded from web sites, or for that would tend to concentrate angling quite nominal costs, they could be loaded pressures from casual anglers in those areas. onto CDs or DVDs for free or very low cost distribution. Some agencies could also 6. Diversify angling regulations and programs partner more extensively with sportsmens’ with respect to, at least, gear, bag limits, or conservation organizations, with the and available species, for these influence latter hosting frequent rural fishing clinics or angler perceptions of the quality of fishing aquatic habitat renovation work days. experiences, whether or not they have an impact on managers’ biological objectives. Roles of hatcheries in fisheries and conservation For example, fly/lure-only or catch-and- release restrictions communicate an agency’s Fishes have been introduced into North desire to develop excellent fisheries for the American waters since at least the 1840’s, with experienced angler. Reduced bag limits widespread distribution of Pacific salmon and trout may affect overall take very little, but they since at least the 1870’s (Ross 1997, Mills et al. 1993, will allow more anglers to approach the Pister 2001). In many locales, stocking of hatchery ‘golden’ limit, perceived (as in par for golf) fishes has enhanced the condition of both sport and as an indicator of personal fishing expertise. commercial fisheries resources and provided greatly Improved and safe access for children to expanded fishing opportunities not supported by local waters with put-take fisheries benefit natural fish production. However, stocked fish have individuals and families not otherwise drawn not always been beneficial, but have contributed to to outdoor sports. Collectively, diversifying widespread decline and sometimes of native fishing opportunities serves a diverse species, altered ecosystem function, and been vectors angling public and trumpets the sensitivity of for the introduction of parasites and disease (Miller agencies to diverse constituent needs, desires, et al. 1989, Williams et al. 1989, Richter et al. 1997, and conditions. Lightfoot 2004).

7. Educate anglers and visitors in ways that Thus, hatchery programs and desires to conserve are more visual, auditory, and kinesthetic wild native resources can come into strong conflict over than one can find in the usual magazines, proposed management actions (Finlayson et al. 2005). brochures, and static displays at many visitor For example, naturalized populations of rainbow trout centers. Static displays at agency offices and compete or hybridize with native cutthroat populations visitor centers could be replaced by touch- throughout Colorado and Wyoming, yet there is screen or trackball controlled computers considerable interest in conserving these naturalized that link directly to existing attractive and populations to meet angler satisfaction. Such competing information-rich web sites for National management goals make it difficult to satisfy angler Forest System lands and state resource demand while protecting native fish populations management agencies. Links to professional and naturalized fish populations simultaneously. quality photographs and videos on these Nonetheless, modern hatcheries continue a tradition of web sites could be supplemented with short attracting considerable public support. They provide a (<3 to 5 minute), topically focused videos visible and esthetically pleasing example of an agency’s or podcasts produced at very low cost by attempts to serve constituents by enhancing fishing students and their teachers from high schools opportunities where they have been reduced by human and colleges. This would be inexpensive, alterations to the land or where such opportunities involve local communities, be highly simply did not exist. visible to local media, expand availability of visually enticing introductions to natural and Issues relating to hatcheries and stocking are human resources, take advantage of readily not restricted to concerns about the fate of native available modern technology and students species. Epifanio (2000) surveyed the 50 states conversant with that technology, increase for their involvement in coldwater fisheries and the breadth of resident and tourist audiences problems that affected those fisheries. Forty-seven for agency programs, and free up agency respondent states managed such fisheries, 38 of which Information and Education employees for indicated that the primary barriers to establishing and 56 57 maintaining self-sustaining populations related to With the advent of concern for declining native habitat. The implications of this finding contrasted species driven by the Endangered Species Act and its sharply with budgets of state management agencies that precursors, as well as the growth in techniques for deemphasized habitat-related programs while pouring hybridization (see examples in Table 12) and genetic many resources into hatcheries and stocking programs. manipulation of fishes, hatchery functions have diversified to include rearing of native species for Clearly, habitat protection and enhancement recovery efforts and special hybrids or strains suitable benefit development of fisheries for native and for introductions into waters with particular habitat , assist with conservation of conditions or fishing demands. In some cases, these threatened taxa, and facilitate development of self- efforts have reduced production capabilities for rainbow sustaining populations of introduced fishes, which may, trout and/or led to improved methods for intensified in turn, reduce reliance on hatchery fish. The USFS and culture of trout. all Region 2 states are active in aquatic habitat research, recovery, and enhancement, reflecting important shifts As noted elsewhere in this assessment, hatchery in concerns about and emphasis on the links between fish are selected for rapid growth in the absence of healthy ecosystems and healthy fisheries. predators, conditions not common in the wild (Biro et al. 2004). Stocked rainbow trout tend to have lower Approaches to stocking hatchery trout: A survival rates than wild trout in nature (Table 13), in major responsibility of fish managers is to see that the part because they are more vulnerable to predation and waters of the state are not overstocked or that stocked may contribute little to reproduction in the wild (Miller fish do not otherwise negatively affect existing fish et al. 2004). Nonetheless, hatchery fish introduced to stocks or native fish populations (Wiley et al. 1993, waters for put-grow-take and put-and-take fisheries Ross 1997). Nonetheless, unpredicted heavy angler where native and naturalized populations already harvest can deplete fish populations, causing agencies reproduce will compete for food resources. Thus, while to turn to a range of compensatory mechanisms to deter hatchery fish have reduced fitness due to low survival the impacts of excessive harvest (Ross 1997). Under and reproduction, they bring increased competition to these and other circumstances, constituent desires native and naturalized populations of the same or other – and sometimes demands – may outweigh biological species and ultimately result in negative consequences considerations. For example, on resident trout. Continued stocking and inbreeding has experienced times when food supply was low might also disrupt adaptations of naturalized and native and competition from nongame fishes was high, so fish to local conditions (Miller et al. 2004). rainbow trout stocking was not justified economically. Nonetheless, stocking continued due to high public The enduring controversy between wild trout demand (Wiley et al. 1993). management and hatchery trout management appears to be a social problem more than a biological problem, Hatchery fishes: Although rainbow trout are the for at the heart of the controversy lie obvious moral focus of this assessment and are the most successfully and economic implications. Early in the 1900’s, the reared and distributed of any coldwater fish worldwide, conventional wisdom was that hatchery stocking of they are only one of many fishes important to hatchery large numbers of fry was essential for maintaining trout and fisheries programs in the Rocky Mountain Region abundance, even where wild populations often existed (Table 12). Rainbow trout rose to dominance in and were reproducing successfully. A general belief coldwater hatchery programs because of their ease of developed over time that hatchery trout can provide culture, ability to tolerate a wide variety of physical, good fishing anytime, ignoring the fact that, given good chemical, and biotic conditions in receiving waters, habitat, natural rainbow trout reproduction produces a and ability to grow to relatively large size (a fact that surplus of young sufficient to eventually recruit into and has also made them valuable for laboratory experiments support even an intense fishery. benefiting from larger fish than animals like goldfish and guppies). During the first half of the 20th century, This faith in hatcheries and stocking has been development of hatchery-rearing systems for rainbow deeply entrenched in both fisheries personnel and trout resulted in rapid development of federal, state, and anglers (Behnke 2004). Derisley Hobbs (1948, cited tribal rearing facilities throughout the United States and in Behnke 2004) studied the effectiveness of stocking other nations, with accompanying introduction of these young trout in New Zealand streams. He argued, and fish into many ecosystems and faunas. was largely ignored, that the number of young trout

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59 Table 12. Fishes raised in Region 2. Data from online state and Federal sources 2006. Species/hybrids # hatcheries (state/fed) Family Genus species (subspecies/strain/hybrid) rock bass 1/0 Ambloplites rupestris largemouth bass 7/1 Centrarchidae Micropterus salmoides black crappie 2/1 Centrarchidae Pomoxis nigromaculatus bluegill 6/1 Centrarchidae Lepomis macrochirus bluegill hybrids 1/0 Centrarchidae Lepomis (bluegill x green sunfish) panfish [NS] 1/0 Centrarchidae [NS] [NS] red ear sunfish 2/0 Centrarchidae Lepomis microlophus smallmouth bass 2/1 Centrarchidae Micropterus dolomieu sunfish hybrids 2/0 Centrarchidae Lepomis [NA] grass carp 3/0 Cyprinidae Ctenopharyngodon idella northern pike 3/0 Esocidae Esox lucius muskellunge 3/0 Esocidae Esox masquinongy tiger muskellunge 1/0 Esocidae Esox (n. pike x muskellunge) hybrid muskellunge 1/0 Esocidae Esox (tiger?) blue catfish 1/0 Ictaluridae Ictalurus furcatus channel catfish 6/0 Ictaluridae Ictalurus punctatus palmetto bass 1/0 Moronidae Morone [NA] striped bass 2/0 Moronidae Morone saxatilis striped bass hybrids 1/0 Moronidae Morone [NA] white bass 1/0 Moronidae Morone chrysops wiper 4/0 Moronidae Morone (white x striped bass) sauger 3/0 Percidae Sander canadensis saugeye 2/0 Percidae Sander [NA] walleye 9/1 Percidae Sander vitreus walleye/sauger hybrid 1/0 Percidae Sander [NA] yellow perch 4/0 Percidae Perca flavescens paddlefish 2/1 Polyodontidae Polyodon spathula Bear River (Bonneville) cutthroat trout 3/0 Salmonidae Oncorhynchus clarkii (utah) Colorado River cutthroat trout 2/0 Salmonidae Oncorhynchus clarkii (pleuriticus) cutthroat trout (subsp. /strain unid.) 1/0 Salmonidae Oncorhynchus clarkii Snake River cutthroat trout 6/2 Salmonidae Oncorhynchus clarkii (bouvieri) Yellowstone cutthroat trout 4/0 Salmonidae Oncorhynchus clarkii (bouvieri) Eagle Lake rainbow trout 6/0 Salmonidae Oncorhynchus mykiss (aquilarum?) Fall rainbow trout 3/0 Salmonidae Oncorhynchus mykiss Firehole rainbow trout 2/0 Salmonidae Oncorhynchus mykiss rainbow trout 8/4 Salmonidae Oncorhynchus mykiss (subsp. /strain unid.) kokanee salmon 5/0 Salmonidae Oncorhynchus nerka chinook salmon 4/1 Salmonidae Oncorhynchus tshawytscha brown trout 10/2 Salmonidae Salmo trutta brook trout 5/0 Salmonidae Salvelinus fontinalis lake trout 3/2 Salmonidae Salvelinus namaycush splake 5/0 Salmonidae Salvelinus (brook x lake) grayling 3/0 Salmonidae Thymallus arcticus state (n = 23) and federal (n = 6) hatcheries. Not an exhaustive list. [NA] - not applicable; [NS] - not specified.

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59 Table 13. Post-stocking survival rates for rainbow trout stocked in North American waters. (Modified from Kerr and Lasenby 2000; additional information and sources listed therein) Waterbody Life Stage Stocked Time from Release Survival Rate (%) Lakes East Fish Lake () — 6 months (October-April) 86% Fox Lake () Fingerlings 4 months 37% Little Bass Lake (Minnesota) Fingerlings 4 months 11% Little Shell Lake (Minnesota) Fingerlings 4 months 18% McCall & MuerlinLakes (Minnesota) Fingerlings 4 months 0% Quemado Lake (New Mexico) Fry Time required to achieve 7.5 9.2% in length Misc. prairie lakes (North Dakota) — 1 month 15-54% Misc. lakes (Michigan and Wisconsin) Age I (yearling) 5 months 32-60% Age II 5 months 15-19% Misc. lakes (Colorado) — — 20-60% Reservoirs Porcupine Reservoir (Utah) Fingerlings 14 months 6.5-7.6% Unnamed Reservoir (Utah) Fingerlings — 39-55% (1987) Fingerlings — 19-25% (1988) Ponds Fuller Pond (Michigan) — 6 months (fall-spring) 50% — 6 months (spring-fall) 10% Streams/rivers Convict Creek (California) Large (2.8-3.7 ) fingerlings 89-151 days 46.6% Small (1.3-1.7 ) fingerlings 89-151 days 44.2% Flint Creek (Montana) Catchables 6 weeks (summer) 83% Overwinter 68% Fool Creek (Wyoming) — 1 year (1974-1975) 41.6-48.5% Little Missouri River (Arkansas) — 5 months 3-10% Platte River drainage (Nebraska) Fingerlings 4-6 months 3.6-54.1% Taylor Creek (California) Fingerlings 1 month 10.6% Three Streams () Fall fingerlings 5 months 1-3% Spring yearlings 3 months 2-7% reared in hatcheries was insignificant compared to the Uses of hatchery fishes - introduction of number of young trout produced naturally. Allen (1951) nonnative species: Introductions of species such as subsequently supported Hobbs’ conclusions about the rainbow trout, brown trout, largemouth bass, striped futility of adding hatchery trout where young wild bass, walleye, and a number of other species and hybrids trout were abundant. Although Allen’s findings did not (Table 12) to new geographic areas to enhance fishing convince fishery managers to stop stocking, they did opportunities have been viewed as successes by many cause wild trout managers in the United States to change game and fish agencies across the country (Ross 1997). from stocking fry and fingerlings to stocking catchable In contrast, conservation biologists argue that nonnative trout (Behnke 2004). This shift has also influenced fish introductions have been irreversibly deleterious public attitudes; for the past 40 years, for example, to the fragile fish communities of the arid West (see Trout Unlimited has tried to shift the focus from put- chapters in Minckley and Deacon 1991), and Richter et and-take fisheries dependent on stocking catchable trout al. (1997) concluded that introductions of exotic species to an emphasis on wild trout management. were the greatest threat to the native aquatic fauna of the western United States. As noted elsewhere in this 60 61 assessment, likely impacts of nonnative species include A relatively recent development for supplemental increased intra- and interspecific competitive and stocking is introduction of sterile triploid rainbow trout. predatory pressures as well as occasional introductions Perhaps the best known cases of stocking of sterile of new parasites and disease. Recovery efforts for native fishes coms from widespread use of triploid grass carp, cutthroat trout in Region 2 have also been compromised a species occurring in each of the Region 2 states, by hybridization with stocked rainbow trout that has led for aquatic weed control. However, sterile triploid to reduction, and in some cases loss, of locally adapted rainbow trout are also appearing in fisheries in some gene complexes in native populations (Kershner et al. western states. Sterility ensures they will not hybridize 1997, Hendrickson et al. 2003). with resident fishes or establish naturally reproducing populations. In addition, they tend to exhibit rapid Uses of hatchery fishes - establishing self- growth and often attain large size; the Washington state sustaining fish populations in new reservoirs and record, almost certainly a triploid fish, weighed 29.6 ponds: Reservoir and pond construction has been pounds. Although we found no reference to federal on the rise since the beginning of the 20th century or state programs that stock triploid rainbow trout (Ross 1997). Maintaining long-term, high quality in Region 2, there are at least two private hatcheries conditions in such systems can be a challenge, as producing or rearing these fish in the Region, and they they often undergo rapid ecological succession with are stocked into at least one private Colorado fishing its accompanying changes in community productivity, lake. Other western states stocking triploid rainbow composition, and structure. These changes can lead to trout include Utah, Idaho, and Washington. boom-and-bust cycles in fish communities, where some species thrive under certain conditions and decline Fisheries supported by stocking - put-and-take as those conditions change. In general, warmwater fisheries:Put-and-take fisheries are designed to provide species (e.g., largemouth and smallmouth bass, crappie anglers with fishing opportunities when self-sustaining and sunfish, yellow perch, catfish), when managed populations cannot be established. Trout are the most with the correct predator-prey balance, commonly common coolwater fishes introduced because they are establish self-sustaining populations in reservoirs and popular among anglers, can be reared to catchable size ponds. Coldwater species, like trout, are less likely to more quickly and at lower cost than other popular sport form self-sustaining populations, in part due to their fishes, and can be grown and available year round (Ross requirements for clean gravel spawning substrates 1997). Even though catchable trout are more expensive preferably swept by currents that are not characteristic to raise, they cost less per fish creeled than subcatchable of most reservoir and pond systems (Ross 1997). Such trout because so few of the latter return compared to substrates may occur in tributaries or in reservoirs with the number planted (Wiley et al. 1993). A reasonable excellent water quality and little sedimentation. In the expectation of return to anglers for a successful stocking Cimarron National Grassland, rainbow trout are stocked program would be at least 50 percent of stocked fish in winter, and fish not harvested are not expected to live (Wiley 2003a). through the hot summer months (Chappell 2006). There are several reasons agencies turn to put- Uses of hatchery fishes - supplementing and-take fisheries. populations: Supplemental stocking has become an integral part of management of numerous salmonid 1. Catchable trout can be stocked to meet heavy populations, both in and out of Region 2. Supplemented short-term angling demands in areas that populations may have been depleted by overharvesting, cannot sustain self-reproducing populations. habitat deterioration, loss of migratory pathways from For example, trout may be stocked in the dam construction, and various other factors. Although spring when angling pressures are on the supplemental stocking is initiated to improve the rise but where waters will be too warm in the abundance of the depleted stock, stocking is often summer months to support a coldwater trout continued after stock recovery has been accomplished fishery. to satisfy increased angler demand (Ross 1997). As noted elsewhere in this assessment, supplemental 2. Fishing can be provided to areas of dense stocking does not enhance the self-sustaining capacity human populations where waters may be of wild populations, but it remains a popular approach polluted or simply not satisfactory to maintain to address depleted populations or to stimulate or long-term fisheries (Ross 1997). Focused support increased angling pressure. urban fishing programs exist in, at least,

60 61 Kansas, Nebraska, and Colorado (as part of per pound stocked in standing waters (trout stocked the latter state’s “Fishing is Fun” program, 1.25-5”, 1300-20/lb). which involves local communities in a three- way partnership with the Colorado Division Fisheries supported by stocking - tailwater of Wildlife and Federal Sportfish Restoration and two-story fisheries: Tailwater fisheries occur Act monies). downstream of dams where cold, clear water is released from the hypolimnion of the reservoir. Because 3. Hatchery trout may shift angling pressures sediment loads are low in hypolimnetic waters and away from wild populations by steering downstream fine sediments are often displaced during anglers toward catchables stocked in the same heavy releases, gravel, cobble, and bedrock substrates water system (Ross 1997). are often exposed and available for colonization by highly productive algae and invertebrates. These 4. Angler satisfaction, at least for less organisms, supported in part by the frequently nutrient- experienced anglers, may be high with put- rich hypolimnetic waters, may allow development of and-take fisheries because stocked fish are robust trout fisheries (McKinney et al. 1999, Simpkins easier to harvest than wild fish. and Hubert 2000). Stocked rainbow trout often can survive to reproductive age, create self-sustaining Programs that stock catchable trout aim to satisfy populations, and grow to large size, but extreme winter recreational demand, stimulate sales of fishing licenses, conditions may lead to high overwinter mortality (Ross and generate excise taxes from purchase of fishing 1997, Annear et al. 2002). equipment and boat fuels. These latter revenues provide a major source of funding for most state fisheries Two-story fisheries occur in lakes or reservoirs that management programs, and by their very nature, they are stratify, providing a warmwater fishery in the epilimnion intended for support of enhanced fishing opportunities and a cool- or coldwater fishery in the hypolimnion. and not simply for conservation of wild resources (Ross For example, Colorado’s Eleven Mile Reservoir on 1997). This can lead to conflicts of interest among the South Platte River contains rainbow, cutthroat, management personnel or agencies, depending on their rainbow-cutthroat trout hybrids, kokanee salmon, and perceived mandates or responsibilities. For example, small populations of brown and mackinaw (lake) trout, the highest numbers of hybrids between rainbow trout as well as warmwater species such as yellow perch, and Colorado River cutthroat trout were found in northern pike, walleye, and smallmouth bass (Gerlich streams that were most recently exposed to stocking 2001). Problems may arise if there is insufficient forage (Kershner et al. 1997). Such put-and-take fisheries with for one of the two fisheries or if seasonal destratification nonnative species have the potential to damage fragile (as in shallow lakes or reservoirs) produces intolerable populations of native fishes, even to the point of local conditions for certain species in the community. The extinction, and they ignore alternative approaches, former circumstance occurs with striped bass in Lake such as development of special native-species fisheries Powell on the Arizona-Utah border, for example, where that could attract considerable angler interest while small striped bass grow rapidly on a gizzard shad satisfying conservation objectives. (Dorosoma cepedianum) diet in the epilimnion but large bass move to a hypolimnion that lacks sufficient Fisheries supported by stocking - put-grow- forage to maintain strong growth or condition. This and-take fisheries: Put-grow-and-take fisheries help led to a recommendation that (Osmerus meet the demand of anglers who seek to harvest fish mordax), native to the north Atlantic and north Pacific, that resemble wild populations. Naive stocked fry or be introduced to serve as a hypolimnetic for fingerlings that survive face the same pressures as wild striped bass (see comments and historical review in trout do as they mature to catchable size, and therefore Minckley 1991). they behave more like wild trout and provide anglers with a more natural fishing experience. These fish are Fisheries supported by stocking - “reclaimed” less costly to rear than catchables and may therefore systems: Reclaimed fisheries for trout are those where reduce program costs if survival to catchable size is management agencies remove existing fishes and high (Ross 1997). Wiley (2003b) belileved that stocking replace them with trout in support of a put-grow-take catchable trout was a success if return to anglers was ≥ fishery or establishment of a self-sustaining population. 1 pound for each pound of fish stocked in streams (for The rationale for such treatments usually focuses on trout 1.25-8” in length, 1300-5 per pound) and 1 pound removal of predators and/or potentially competitive

62 63 or otherwise undesired “nuisance” species, leaving the Fun” applications for funding from urban communities waters free for development of trout fisheries. will receive high priority. or antimycin are the most common ichthyocides used to remove species present. Because treated waters These types of programs share several lack most potential predators or competitors, small somewhat distinctive characteristics compared to subcatchable trout should experience excellent survival management schemes in more natural waters. Urban and keep program costs low (Ross 1997). fishing programs introduce catchable size fish into existing lakes and ponds found in parks and other Reclaiming systems for trout fisheries can create areas of human population centers. Because such sustainable fisheries in waters perceived to need systems frequently experience considerable seasonal rehabilitation. However, managers must carefully temperature variation, urban programs in the western assess the presence or absence of native fishes and states stock trout in the cool periods and catfish or develop objectives and methods with great care. A other warmwater species in warmer periods. This rotenone treatment of the Green River in preparation for and frequent and often widely publicized stocking developing a trout fishery in Flaming Gorge Reservoir schedules ensure year-round fishing opportunity and affected native fish populations in more than 800 km of virtually guarantee intense fishing pressure and high the river and its tributaries and well downstream of the public visibility. States differ in the funding sources target area (Holden 1991). for such programs and the sources of fish for stocking. In some cases, a state fishing license allows access to Urban fisheries: Although not applicable to both urban and rural fishing opportunities while in other management of rainbow trout in Region 2 national forests states (e.g., Arizona) a separate license is required for and grasslands, regional managers should be aware of urban fishing. Similarly, in some states, stocked fish the growing application of stocked rainbow trout to are produced in state hatcheries while in others (e.g., existing urban waters in a variety of U.S. cities. Of the Arizona) stocked fish are purchased from commercial five states of the Rocky Mountain Region, Kansas and suppliers. Minimum size of fish may be designated, and Nebraska have well-developed urban fishing programs a few much larger fish are often added to each load of at this time, and there has been recent approval for such fish to increase attractiveness to anglers. a program in Colorado as part of their “Fishing is Fun” program. In Kansas, 77 lakes are currently stocked with Such programs have many benefits. When 3/4- to 1 1/2-pound channel catfish, hybrid sunfish, and managed properly, they bring considerable positive wipers every few weeks from April through September visibility to agencies from segments of the population (http://www.kdwp.state.ks.us). This program serves all often not knowledgeable about natural resources or Kansas metro areas with populations exceeding 40,000 their management, clearly demonstrating an agency’s that have public fishing waters. Garden City provides concern for all of their various constituencies. In the only urban program close to a Region 2 facility addition, urban sites add a valuable and different (Cimmarron National Grassland). Nebraska’s Urban dimension to existing inner-city or suburban recreation Fishing Program (UFP) (http://www.ngpc.state.ne.us) opportunities, and they tend to bring a diverse array of currently lists about 75 potential program sites in 55 people together. They also have been used effectively cities across Nebraska, with sites added as the Nebraska for special youth fishing programs where children learn Game and Parks Commission’s Aquatic Habitat about resources and management and are taught to fish, Program works to improve lake and pond habitat in often using agency equipment. conjunction with the Nebraska Environmental Trust Fund and the Nebraska Department of Environmental Factors influencing survival and reproduction Quality. Catchable size channel catfish and trout of stocked fish: Many factors influence the return rate are stocked to provide fishing opportunities to more of stocked trout (Kerr and Lasenby 2000). Attempts to anglers. In some lakes, stocking frequency has been establish reproducing and eventually self-sustaining increased to meet demand, and additional fish species populations should consider factors listed elsewhere in have been stocked to diversify opportunity in a few this assessment as necessary for successful reproduction locations. While the Nebraska UFP works primarily on as well as survival and growth of all life history smaller (<100 acres) lakes and city park ponds, streams stages. When fish are stocked into waters where life and rivers flowing through urban areas may also be expectancy is short due to intense angling pressure or included in program activities in the future. Finally, marginal conditions, constraints are relaxed because Colorado’s Wildlife Commission recently approved a rainbow trout exhibit greater tolerance for many water resolution to promote urban fishing access. “Fishing is quality variables (e.g., salinity, pH, temperature) than 62 63 many other salmonids. Nonetheless, factors affecting wetted area of the streambed, water velocity, suspended post-stocking success should be considered. Four solids, and the rates and locations of bed scour and factors, each discussed below in detail, include habitat sediment deposition (Crisp 1993); all of these may sufficiency, stocking practices, emigration of stocked affect survival of one or more life history stages. High fish, and anglers. and low seasonal flows and ice appear to limit survival and return of subcatchable trout more than catchable Habitat sufficiency - hysical habitat: As noted trout. Trout in shallow standing waters (i.e., shallow elsewhere, habitat requirements differ among life history lakes, ponds) are susceptible to high temperatures and stages. While types of habitat required for spawning accompanying low dissolved oxygen during summer and rearing through the fry stage may be a concern only periods, while complete winter ice cover may lead when attempting to establish an actively reproducing to hypoxic and even anoxic conditions and winter population, stocking of subcatchables and catchables fish kills. Artificial aeration or water circulation may should occur where they can form aggregations in deep overcome both conditions to various degrees. pools or disperse into more complex cover and feed sufficiently to support survival. Habitat sufficiency - productivity of receiving waters: Receiving waters must have sufficient food Habitat sufficiency - water quality: The standing crops to support introduced trout over the chemistry (e.g., salinity, osmolarity, dissolved oxygen) short term and sufficient primary production (or of receiving waters should be similar to that of allochthonous input in lower order streams; Vannote hatchery or transport water. Hatchery fish have failed et al. 1980) and secondary production to ensure a to survive in waters where total dissolved solids vary sufficient trout food supply in the long term. Strong greatly from hatchery to receiving waters. Lakes and seasonality of and other trout food production and streams, particularly in urban areas, receive a variety the frequently accompanying curtailed growing season of chemical pollutants. Low dissolved oxygen levels at high altitudes and high latitudes should be considered in waters that are warm, polluted, or otherwise have in developing stocking strategies for trout. high levels of respiratory activity may be tolerable for post-emergent life history stages, but they may slow Habitat sufficiency - resident stocks of trout development, cause premature or delayed hatching or other competing or predatory fishes: As noted of eggs, and lead to reduced size of hatchling sac fry elsewhere, interactions of rainbow trout with resident (Bjornn and Reiser 1991). fishes, particularly in Colorado and Wyoming with extensive coolwater habitat and established native and Habitat sufficiency - water temperature: introduced faunas, may take several forms. Susceptibility Receiving waters should have temperatures similar to to resident predators will be highest shortly after hatchery or transport water temperatures. Significant stocking when new animals are disoriented, stressed, temperature shock during stocking may alter naïve, and concentrated in a small area. Competition for responsiveness, swimming ability, or other behavioral fundamental resources such as food, feeding sites, and functions in the short term and affect physiological refuge or resting sites may be most intense immediately functions in the long term as the animal acclimates to the after stocking, occur at any time of year, be intra- or new temperature. Given the many effects of temperature interspecific, and be either exploitative or contest in on fishes, in-stream temperature regulation is a common nature. For example, some of Wyoming’s waters lack management issue. Stream temperature can be altered an adequate food supply to support wild populations, by removal of stream bank vegetation, withdrawal and and management strategies recognizing this have return of agricultural water from irrigation, releases proven successful at providing a decent fishery (Wiley from cold and deep or warm and near-surface waters et al. 1993). Predictably, subcatchable trout suffer lower of reservoirs, and cooling of nuclear and other power survival under such conditions, leading managers to plants (Bjornn and Reiser 1991). conclude that subcatchables should only be stocked into lakes where density of piscivorous species is low Habitat sufficiency - water quantity: Fish and competition for food with non-game species is should be stocked into streams where extreme light. In contrast to the recurring and complex nature of fluctuations in discharge, either natural or regulated, competition over resources required for all size groups are unlikely or where sufficient habitat (e.g., deep of trout, competition for spawning sites and mates will pools for summer and winter refuge, cover, refuges be seasonal, potentially intense, contest in nature, and from strong currents) remains during normal seasonal involve both conspecifics and other salmonids. extremes of flow. Changes in flow regime directly affect 64 65 Habitat sufficiency - hatchery conditions: Stocking practices - note on stocking Hatchery rearing practices will influence physiological, terminology: Various agencies have applied an array of anatomical, and behavioral traits of rainbow trout. stocking prescriptions, so managers seeking to compare Hatchery diets support rapid growth and generally good published alternatives face potential confusion from the condition and nutritional status. Body composition variety of terms used to describe stocked fish (Table 14; may change with altered diet over the short term Kerr and Lasenby 2000). These terms include number (Gelineau et al. 2002, Yamamoto et al. 2002), and body of individuals, age (e.g., young-of-the-year, Age I, composition may influence performance of interest Age II, yearling), body size (e.g., fingerling, catchable, to managers (e.g., overwinter survival, swimming subcatchable, total (TL) or fork length (FL), number of performance; Gregory and Wood 1998). As noted fish per pound), and life history stage (see section in elsewhere, purposeful and accidental selection can alter this assessment). Interpretation of stocking data may several other performance variables. require managers to develop algorithms that allow at least approximate transformations among various Habitat sufficiency - genetic strain: Intense quantitative descriptors. artificial selection has produced a variety of rainbow trout strains, each with characteristics intended to Stocking practices - time of stocking: In general, enhance performance in specific ecological or hatchery spring or early summer stocking, when stocked fish conditions (and probable unintended characteristics encounter periods of rich food supplies and survivors resulting from selection associated with high density can explore habitat and insert themselves into existing rearing) (Myrick 1999, Myrick and Cech 2000). social systems, generates higher rates of return than Traits of rainbow trout that exhibit genetic influence fall stocking does (Kerr and Lasenby 2000). Wiley include physiological characteristics (growth, disease/ et al. (1993) suggested that subcatchables, if stocked parasite resistance, age at maturation), behavioral in streams at all, should be stocked immediately after traits (movements, swimming ability, general ease of spring runoff to avoid subjecting these fish to excessive handling, general activity and feeding rates), and traits and turbid flows and to take advantage of rich spring influenced by an animal’s physiology, behavior, and and early summer foods to support rapid growth. ecology (e.g., survival, catchability, and contributions to Subcatchables stocked in fall exhibited low survival fisheries) (Kerr and Lasenby 2000, Valente et al. 2001). and return; fewer than 10 percent of the catchable trout For example, ten years of spawning-date manipulations stocked in the fall returned, and these generally did not produced a trout that spawned over 60 days in advance survive to the second season. Similarly, where there are of its original date (Gall 1998), expanding the time of multiple stockings in the same location during a fishing year when eggs or fingerlings can enter the production season, returns tend to be greater with early-season than system and respond to a year-round market demand for with late-season stocking. rainbow trout (Siitonen and Gall 1989). Stocking practices - size at stocking: Small Habitat sufficiency - transport stress: Fish trout are more susceptible to predation or competition arriving at a stocking site have undergone a series of from larger fish than larger trout are. For example, stressful conditions that should be minimized when comparison of return rates for catchable trout in lakes possible (Dunlop et al. 2004). Capture at the hatchery (47 percent) and streams (27.5 percent) with return generally involves concentration in raceways with a rates for subcatchable trout of 8 percent in lakes and seine or other barrier that leads to increased fright, 6 percent in streams indicated that subcatchables did decreased inter-individual distance, and increased not meet management standards for return rates in abrasion. Fish may be moved to transport tanks by a Wyoming system (Wiley et al. 1993). In Crystal net, mechanical suction, or conveyor, all accompanied Reservoir, stocked catchable trout had return rates of by exposure, additional abrasion, and eventual almost 90 percent, probably because larger trout escape immersion into water that may differ in temperature predation more successfully than smaller trout, fewer and composition to the original raceway. Transport fish need rely on a limited food supply, and anglers keep extends the period of stress and may increase its and report larger fish rather than practice catch-and- severity due to vibration and dense packing of fish. release with small fish. Finally, stocking places stressed animals through yet another sequence of handling and introduction into an Stocking practices - number of trout stocked extremely foreign environment. and stocking rates: Stocking rates vary considerably

64 65 Table 14. Summary of rainbow trout stocking rates reported in various North American jurisdictions. Water body Age/size category Per acre - Per ha Per meter or mile Ponds fry 350-1000 fingerlings 200-500 Lakes fry 1500 16,000-64,000/mi shoreline fingerlings 30-150 200/mi shoreline yearlings 2-150 100-350/mi shoreline subcatchables 20-30 catchables 10, 150-300 “fish” 25-75 Streams fry 450/m fingerlings 100-200 60/m yearlings 50-100, 50-150 30/m, 15/m Extracted from Kerr and Lasenby 2000. For more focused specific recommendations incorporating measures of fishing effort and biological productivity in Wyoming, readers should see Wiley 2003b. among different jurisdictions according to desired yield, stocking practice (density, especially overstocking), and survival, desired mean weight per fish in the catch, characteristics of stocked fish (genetic strain). competing species, habitat type, size of trout available, expected fishing pressure, fish abundance in the Anglers: Anglers vary considerably in their receiving water, and productivity of the system (Table primary motivations for fishing and thus in their 14). While there are no universally applicable guidelines potential impact on trout populations and their for trout stocking, Kerr and Lasenby (2000) provide likelihood to fish local vs. remote waters or stocked vs. an extensive list of approaches used to determine the wild fish. “Social anglers” enjoy time spent with friends number and size of rainbow trout to be stocked in various and/or family while “nature anglers” are most interested North American standing and flowing waters. In some in enjoying the outdoors. For the “relaxation anglers,” cases, relatively simple data sets can direct stocking fishing provides an opportunity to escape everyday tactics. Hubert et al. (1996), for example, developed a pressures and relax as opposed to the “excitement model based on percent cover, elevation, late summer anglers” for whom fishing provides an opportunity for wetted stream width and channel gradient to calculate excitement. “Food anglers” are primarily motivated predicted mean biomass (PMB) of trout supportable by by the opportunity to bring fish home to eat, and Wyoming streams, information potentially valuable in “sports anglers” seek to catch a trophy fish, become determining subsequent stocking practices. Regardless a proficient angler, or compete with other anglers in of the approach used to determine stocking densities, fishing tournaments. there is always a potential for overstocking. Mortality rates of hatchery-reared rainbow trout may increase Information Needs substantially with an increase in stocking density (Kerr and Lasenby 2000). As previous sections of this assessment verify, many aspects of the biology of rainbow trout in nature Emigration of stocked fish: Movements of are well documented, as are topics relating to rainbow recently stocked fish from targeted recipient waters may trout hatchery production, introductions outside their interfere with achievement of management objectives. range, impact on native species, and various aspects of In their review of rainbow trout stocking programs, their physiology, genetics, cell biology, and diseases. In Kerr and Lasenby (2000) list factors that have been general, the biological information necessary to develop demonstrated to influence post-stocking movements strong management plans is available. The major issues of trout, including water quantity (elevated discharge appear to relate more to interspecific conflicts with or flooding, reductions in water levels) and quality native species, education of constituents, and creativity (water temperatures, formation of frazil ice, pollution), in management practices than to insufficient knowledge 66 67 about rainbow trout biology. There are several key needs where supplementation is desired, natural for additional information that would ease development productivity of many aquatic environs could of management practices consistent with modern support put-grow-take fisheries dependent on ecosystem management and conservation biology. fingerling or fry stocking.

1. As indicated elsewhere, evidence indicates 4. As additional wild trout restoration efforts are that introduced rainbow trout have exerted developed, educational programs directed at negative impacts on native salmonids and anglers and outfitters should be developed and other fishes. In many cases, the actual distributed widely. These should be assessed nature (e.g., predation, competition) and to see if they prevent situations where intensity of the impacts is unclear; simple anglers sabotage these efforts with illegal overlap in resource use or a species of stocking (Williams 2002) or reduce charges concern recorded from a trout stomach are that agencies are trying to put outfitters out insufficient to establish the type or level of of business with protective programs like threat. While most managers rarely possess catch-and-release that, in the long run, create the luxury of time to perform laboratory sustainable fisheries and enhanced fishing or field experiments, urging (and funding) opportunities. The restoration of cutthroat such studies by agency research personnel, trout in and catch-and- interns, students, or college and university release regulations generated $36 million for faculty could provide managers with much- local business owners in 2002. The value of needed tools. For example, demonstration these actions in Yellowstone Lake was later of competition virtually requires carefully compromised by an illegal stocking of lake designed experiments, yet Weber and Fausch trout, a large predator capable of virtually (2003) found few studies sufficiently rigorous eliminating cutthroat trout from the system to test for presence of competition between (Williams 2002). wild and stocked salmonids. Similarly, descriptions of diets based on stomach 5. Efforts should be continued to understand, or intestinal contents may be misleading educate, and work with both consumptive and without measures of food availability (e.g., non-consumptive users about conservation standing stock, periodicity of availability) or and management needs and tactics. Such periodicity and frequency of feeding. efforts must incorporate the literature on learning styles of constituents and produce 2. Reassessment of stocking programs could educational instruments to match those lead to greater efficiency in management of learning styles. Conflicts with constituents both hatcheries and fish in the wild. Stocking may arise when interested parties (e.g., programs thought to be necessary when begun individuals, non-governmental organizations) may lead to expectation of their continuance do not understand the problem at hand or the by constituents even though they are methods available to managers for dealing unnecessary. For example, Montana stopped with that problem that are practical and both stocking brown trout and rainbow trout in a biologically and cost effective. section of the Madison River where these fish were long established (Vincent 1987, Rainbow trout are unusual among western fishes Williams 2002). Within four years, numbers in that their widespread distribution through many of fish three years of age and older increased types of habitats, their visibility to both consumptive by 942 percent. Such experiments may meet and non-consumptive users, and their nonnative status with angler resistance if not accompanied by virtually ensure constituent and political involvement educational programs. in what for most other fishes would be biological decisions. In addition to being central in the native- 3. In some systems, stocking catchable size vs.-nonnative conflict, they also figure heavily in the trout is not justifiable nor does it create economics of sport fishing and aquatic habitat support. value. Low intensity fisheries on mountain The average angler spends over $1,200 per year on the streams, for example, may well be supported sport, contributing an estimated $116 billion overall by natural reproduction and growth of trout, to the economic output in the United States. The eliminating the need for any stocking. Even supports over one million jobs and 66 67 over $30 billion in wages, generating more revenues participation exceeded angling participation in than large corporations like Nike, Ford, or Microsoft South Dakota (U.S. Fish and Wildlife Service 2006). (www.sdgfp.info). As recruitment of new hunters Although millions of dollars are spent each year on declines (Flather and Hoekstra 1989) and interest in native cutthroat and other native fish restoration efforts, fishing increases, agency focus may change. Resident rainbow trout will hold a critically important position in angler participation exceeded hunter participation in state resource management well into the near future. Colorado, Wyoming, Nebraska, and Kansas; hunting

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